Method for observing magnetic domains in a steel plate

Abstract

To easily obtain highly accurate information as information about a magnetic domain structure in a steel material.SOLUTION: A magnetic domain observation method in a steel plate creates a reflection electron image including at least one of an upper reflection electron image and a lower reflection electron image and a left reflection electron image and a right reflection electron image by creating a reflection electron image of a sample S for each region of at least a portion on the upper, lower, right and left sides with respect to the center of an EBSD detector 120, creates an X-direction magnetic domain contrast enhanced image and a Y-direction magnetic domain contrast enhanced image as the reflection electron images in which the magnetic domain contrast in the ±X direction or the ±Y direction is enhanced and the irregularity contrast is alleviated in comparison to the reflection electron image, and acquires a magnetic domain structure of the sample S by using the created X-direction magnetic domain contrast enhanced image and Y-direction magnetic domain contrast enhanced image.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for observing magnetic domains in a steel sheet.

Background Art

[0002] In electromagnetic steel sheets, it is required to achieve low iron loss characteristics and control the noise problem caused by magnetostriction. Iron loss is the power loss consumed as heat energy when the iron core is excited by an alternating magnetic field, and from the perspective of energy conservation, it is required that the iron loss be as low as possible. Magnetostriction refers to the fact that when an electromagnetic steel sheet is excited by an alternating current, the outer shape of the electromagnetic steel sheet slightly changes as the magnetization strength changes, and it is expected that this causes the electromagnetic steel sheet to vibrate and lead to noise. To control these magnetic properties, it is known that it is important to control the crystal orientation and magnetic domain structure in the electromagnetic steel sheet. Therefore, analytical methods and devices for analyzing the crystal orientation and magnetic domain structure are required. In particular, in grain-oriented electrical steel sheets, an aggregate structure called the GOSS orientation is developed. However, if it deviates from the GOSS orientation, lancet magnetic domains are generated according to the deviation angle, resulting in deterioration of magnetic properties. Therefore, detailed knowledge about the relationship between the crystal orientation and the magnetic domain structure is required.

[0003] As a method for observing the magnetic domain structure, in Patent Document 1, the so-called Bitter method is used. The Bitter method is a technique in which a liquid containing magnetic colloid particles is applied onto a magnetic material and dried, and then the particle positions are observed. It utilizes the property that magnetic colloid particles gather at the magnetic walls. By observing the particle positions after drying, the magnetic wall positions can be known, and thus knowledge about the size of the magnetic domains can be obtained.

[0004] As a method capable of determining not only the size of the magnetic domains but also the magnetization direction within the magnetic domains, in Patent Document 2, a magnetic domain observation method using a Kerr effect microscope using the magneto-optical Kerr effect has been proposed. In a Kerr effect microscope, while the in-plane two-dimensional magnetization direction of the observation surface can be observed, information regarding the crystal orientation cannot be obtained.

[0005] In Patent Document 3, a method is disclosed in which an inclined sample is irradiated with an electron beam to obtain a reflected electron image, and a magnetization component parallel to the direction orthogonal to the inclination axis is observed as magnetic domain contrast. With this method, it is possible to observe magnetic domains by using an electron beam, but similar to Patent Document 2, information regarding crystal orientation cannot be obtained simultaneously.

[0006] On the other hand, in Non-Patent Document 1, a method is disclosed in which information regarding crystal orientation is obtained from an electron backscatter diffraction (EBSD) image obtained by inclining a sample and irradiating it with an electron beam in a scanning electron microscope, and magnetic domain contrast is obtained by constructing a reflected electron image from the image luminance of the EBSD image. By using this method, it is possible to relate the distribution of magnetic domains in the observation region to the crystal orientation. However, the technique of Non-Patent Document 1 has a problem in that information regarding the magnetization direction within the magnetic domain cannot be obtained.

[0007] In general, reflected electron images and secondary electron images obtained with a scanning electron microscope include contrast due to the unevenness of the sample surface. For this reason, the contrast due to the unevenness overlaps with the contrast due to the magnetic domains, making it difficult to distinguish the contrast due to the magnetic domains. In order to prevent this, it is necessary to prepare the sample surface to be flat and free from surface damage due to sample adjustment. However, in reality, some degree of unevenness formation on the sample surface is inevitable.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

Patent Document 3

Non-Patent Documents

[0009]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0010] As described above, conventionally, it has not been easy to obtain highly accurate information regarding the magnetic domain structure (the size of magnetic domains and the magnetization direction within magnetic domains) in a steel plate. An object of the present invention is to enable easy acquisition of highly accurate information regarding the magnetic domain structure in a steel material.

Means for Solving the Problems

[0011] The steel plate is iron having a body-centered cubic (BCC) structure, and by utilizing the property that the magnetization direction is parallel or anti-parallel to the <100> direction and adjusting the surface of the sample to the (001) plane, the candidates for the magnetization direction within the analysis plane are limited to four directions, namely, the

[0100] , [-100],

[0010] , [0-10] directions. As a result of intensive studies by the present inventors, it has been found that a method for discriminating the magnetization direction can be constructed by constructing a reflected electron image from the pixel intensity in a specific region of the EBSD image and changing the magnetic domain contrast within the reflected electron image. The gist of the present invention is as follows. [1] An electron beam is irradiated onto a measurement point of a sample composed of a steel plate having a BCC (Body Centered Cubic) structure within an electron microscope, and an EBSD (Electron BackScatter Diffraction) image showing the diffraction pattern of the reflected electrons reaching an EBSD detector is used to observe the magnetic domains and magnetization direction in the steel. This is a method for observing magnetic domains in a steel plate. Board ​In the EBSD detector, when the electron beam is projected onto the EBSD detector, a direction parallel to the irradiation direction of the projected electron beam is defined as the irradiation parallel direction, a direction antiparallel to the irradiation parallel direction is defined as the irradiation antiparallel direction, and two mutually antiparallel directions perpendicular to the irradiation parallel direction are defined as the first irradiation side direction and the second irradiation side direction, respectively. A sample adjustment step of adjusting the sample so that the sample surface corresponds to the (001) plane of the BCC structure. A sample setting step of setting the sample in the electron microscope such that the

[0100] direction and the [-100] direction of the crystal correspond to one of the irradiation parallel direction, the irradiation antiparallel direction, the first irradiation side direction, and the second irradiation side direction, and the

[0010] direction and the [0-10] direction of the crystal correspond to the other. A first backscattered electron image creation step of creating a backscattered electron image in a partial region of the EBSD image by calculating the intensity of backscattered electrons in a partial region of the EBSD image for the sample set in the sample setting step while varying the measurement points. A second backscattered electron image creation step of creating a backscattered electron image in which the contrast derived from magnetic domains having magnetization directions corresponding to the

[0100] direction and the [-100] direction and the contrast derived from magnetic domains having magnetization directions corresponding to the

[0010] direction and the [0-10] direction are emphasized and the contrast derived from the shape of the sample surface is relaxed based on the backscattered electron image created in the first backscattered electron image creation step. A magnetic domain structure acquisition step of acquiring information indicating the size, shape, and magnetization direction of each magnetic domain in the sample using the backscattered electron image created in the second backscattered electron image creation step. having In the first reflected electron image creation step, at least one of the reflected electron image on the anti-irradiation parallel direction side, which is a reflected electron image in at least a part of the region on the anti-irradiation parallel direction side of the EBSD image with respect to the position corresponding to the measurement point, and the reflected electron image on the irradiation parallel direction side, which is a reflected electron image in at least a part of the region on the irradiation parallel direction side of the EBSD image with respect to the position corresponding to the measurement point, and the first irradiation side direction reflected electron image, which is a reflected electron image in at least a part of the region on the first irradiation side direction side of the region of the EBSD image with respect to the position corresponding to the measurement point, and the second irradiation side direction reflected electron image, which is a reflected electron image in at least a part of the region on the second irradiation side direction side of the region of the EBSD image with respect to the position corresponding to the measurement point, are created. A method for observing magnetic domains in a steel plate. [2] In the first reflected electron image creation step, the reflected electron image on the anti-irradiation parallel direction side, the reflected electron image on the irradiation parallel direction side, the first irradiation side direction reflected electron image, and the second irradiation side direction reflected electron image are created. The method for observing magnetic domains in a steel plate according to [1]. [3] In the second reflected electron image creation step, by performing addition of the pixel value of the reflected electron image on the anti-irradiation parallel direction side and the pixel value of the reflected electron image on the irradiation parallel direction side, a first irradiation direction magnetic domain contrast enhanced image, which is a reflected electron image in which the contrast derived from a magnetic domain having a magnetization direction corresponding to one of the

[0100] direction and the [-100] direction and the

[0010] direction and the [0 - 10] direction is enhanced and the contrast derived from the shape of the sample surface is relaxed, is created, and by performing subtraction of the pixel value of the first irradiation side direction reflected electron image and the pixel value of the second irradiation side direction reflected electron image, an irradiation side direction magnetic domain contrast enhanced image, which is a reflected electron image in which the contrast derived from a magnetic domain having a magnetization direction corresponding to the other is enhanced and the contrast derived from the shape of the sample surface is relaxed, is created. The method for observing magnetic domains in a steel plate according to [2]. [4] The above FirstIn the reflected electron image creation step, the irradiation anti-parallel direction side reflected electron image, the first irradiation side direction side reflected electron image, and the second irradiation side direction side reflected electron image are created, and the irradiation parallel direction side reflected electron image is not created. The method for observing magnetic domains in a steel sheet according to [1]. [5] In the second reflected electron image creation step, after adding the pixel values of the first irradiation side direction side reflected electron image and the pixel values of the second irradiation side direction side reflected electron image, subtracting the pixel values of the irradiation anti-parallel direction side reflected electron image is performed. Thus, a second irradiation direction magnetic domain contrast enhanced image is created, which is a reflected electron image in which the contrast derived from magnetic domains having a magnetization direction corresponding to one of the

[0100] direction and the [-100] direction, and the

[0010] direction and the [0-10] direction is enhanced, and the contrast derived from the shape of the sample surface is relaxed. By subtracting the pixel value of the first irradiation side direction side reflected electron image from the pixel value of the second irradiation side direction side reflected electron image, an irradiation side direction magnetic domain contrast enhanced image is created, which is a reflected electron image in which the contrast derived from magnetic domains having a magnetization direction corresponding to the other is enhanced, and the contrast derived from the shape of the sample surface is relaxed. The method for observing magnetic domains in a steel sheet according to [4]. [6] In the first reflected electron image creation step, among the divided regions obtained by dividing the region of the EBSD image into a plurality of regions such that at least three regions exist in each of the directions corresponding to the irradiation parallel direction and the irradiation anti-parallel direction, and the directions corresponding to the first irradiation side direction and the second irradiation side direction, without using the pixel values of the divided region closest to the position corresponding to the measurement point in the EBSD image, using the pixel values of the divided region closest to the edge of the EBSD image, reflected electron images in a partial region of the EBSD image are created respectively. The method for observing magnetic domains in a steel sheet according to any one of [1] to [5]. [7] The reflected electron image created in the first reflected electron image creation step is an image including the observation region of the crystal orientation of the sample analyzed based on the EBSD image. The information indicating the size, shape, and magnetization direction of each magnetic domain in the sample is information on a region including the observation region of the crystal orientation of the sample. The method for observing magnetic domains in a steel sheet according to any one of [1] to [6].

Advantages of the Invention

[0012] According to the present invention, highly accurate information can be easily obtained as information on the magnetic domain structure in a steel material.

Brief Description of the Drawings

[0013]

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Mode for Carrying Out the Invention

[0014] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In addition, regarding length, position, size, interval, etc., when the comparison targets are the same, it includes not only the case where they are exactly the same, but also those that are different within the range not departing from the gist of the invention (for example, those that are different within the tolerance range determined during design). Also, in each figure, the symbol showing ● inside 〇 indicates from the back side to the front side of the test. For example, when a symbol showing ● inside 〇 is attached beside +X, it indicates that the +X direction is the direction from the back side to the front side of the paper surface.

[0015] FIG. 1 is a diagram showing an example of the configuration of an analysis system that performs EBSD analysis. FIG. 2 is a flowchart explaining an example of a method for observing magnetic domains in a steel sheet.

[0016] In FIG. 1, the analysis system is a system for observing (analyzing) magnetic domains and magnetization directions in a steel sheet having a BCC structure. In the present embodiment, the case where the steel sheet is a non-oriented electrical steel sheet is exemplified, but the steel sheet is not limited to a non-oriented electrical steel sheet. For example, it may be a grain-oriented electrical steel sheet or an isotropic electrical steel sheet, or may not be an electrical steel sheet. The analysis system includes a scanning electron microscope 110, an EBSD detector 120, an imaging device 130, and an information processing device 140.

[0017] When the sample S is a steel plate having a BCC structure, the easy axis of magnetization of iron is parallel to the principal axis of the crystal, and the magnetization direction in one magnetic domain in iron is limited to any of the directions of

[0100] , [-100],

[0010] , [0-10],

[0001] , and [00-1]. Furthermore, if the surface of the sample S is limited to the (001) plane, the magnetization directions observable from the surface of the sample S are limited to only the directions of

[0100] , [-100],

[0010] , and [0-10]. Therefore, the sample S is adjusted so that the surface of the sample S corresponds to the (001) plane (sample adjustment step in step S201). In order for the surface of the sample S to correspond to the (001) plane, the crystal orientation of the sample S to be observed is measured in advance by the EBSD method or the Laue method using X-rays, and the surface of the sample S may be prepared (processed) so that the (001) plane becomes the surface of the sample S. Since the original magnetic domain structure changes if there is processing strain on the surface of the sample S, it is preferable to perform a finishing process to remove the surface processing strain using electrolytic polishing or the like. Also, it is preferable to suppress the deviation angle from the (001) plane to about ±5°. This is because if the deviation angle becomes large, a leakage magnetic field is generated on the surface of the sample S, and the magnetic domain structure on the surface of the sample S may change significantly. Thus, not only does the surface of the sample S become completely parallel to the (001) plane, but such a deviation is also tolerated. That the surface of the sample S corresponds to the (001) plane means not only that the surface of the sample S becomes completely parallel to the (001) plane, but also that such a deviation may be tolerated.

[0018] EBSD analysis is carried out inside a scanning electron microscope 110. An electron beam probe EP is focused and scanned by an optical system 111 inside the scanning electron microscope. The optical system 111 inside the scanning electron microscope includes an electron gun, a focusing lens, a scanning deflector, etc. The optical system 111 inside the scanning electron microscope is not particularly limited as long as it is installed in a commercially available known scanning electron microscope. The sample S is set on a sample holder 112 such that its surface (the surface irradiated with the electron beam probe EP) faces the optical system 111 and the EBSD detector 120, and is inclined with respect to the electron beam probe EP generated from the optical system 111 (sample setting step in step S202). In FIG. 1, a case where the inclination angle θ is the inclination angle with respect to the horizontal plane (the installation surface of the scanning electron microscope 110) is illustrated. Although an inclination angle θ of 70° is generally used as the inclination angle for clearly obtaining a diffraction pattern (Kikuchi pattern) in the EBSD method, an angle of about 40 to 80° is also acceptable.

[0019] In FIG. 1, a case where the irradiation direction of the electron beam probe EP is vertically downward is illustrated. Here, when the electron beam probe EP is projected onto the EBSD detector 120 (the detection surface of the backscattered electrons BE), a direction parallel to the irradiation direction of the projected electron beam probe EP is defined as the irradiation parallel direction, and a direction antiparallel to the irradiation parallel direction is defined as the irradiation antiparallel direction. That is, the irradiation parallel direction is, for example, the direction in which a normal projection vector obtained by orthogonally projecting the vector regarded as the traveling direction vector of the electron beam probe EP onto the EBSD detector 120 (the detection surface of the backscattered electrons BE) points. Also, two mutually antiparallel directions perpendicular to the irradiation parallel direction are defined as the first irradiation side direction and the second irradiation side direction, respectively. In FIG. 1, a case where the EBSD detector 120 is arranged such that the EBSD detector 120 is parallel to the electron beam probe EP is illustrated. Also, a case where the EBSD detector 120 is arranged along the vertical direction (vertically up and down direction) is illustrated. Therefore, projecting the electron beam probe EP onto the EBSD detector 120 corresponds to translating the electron beam probe EP parallel to the position of the EBSD detector 120. Thus, the direction parallel to the irradiation direction of the electron beam probe EP projected onto the EBSD detector 120 (irradiation parallel direction) is downward (vertically downward), the irradiation antiparallel direction is upward (vertically upward), and the first irradiation side direction and the second irradiation side direction are the left and right directions. More specifically, in the present embodiment, when looking at the sample S side through the EBSD detector 120 with the irradiation antiparallel direction (upward) as up, the left direction is defined as the first irradiation side direction, and the right direction is defined as the second irradiation side direction. In FIG. 1, the downward direction (vertically downward) is the direction of the tip side of the traveling direction of the electron beam probe EP (the direction indicated by the straight line showing the electron beam probe EP), and the upward direction (vertically upward) is the opposite direction. Also, the direction from the front side toward the back side facing the paper surface of FIG. 1 is the left side, and the direction from the back side toward the front side is the right side. In the following description, up, down, left, and right are as expressed above.

[0020] In addition, when the EBSD detector 120 (the electron beam detection surface thereof) is in a state parallel to the electron beam probe EP, the direction parallel to the irradiation direction of the electron beam probe EP on the EBSD detector 120 (the electron beam detection surface thereof) is defined as the irradiation parallel direction, and the irradiation parallel direction, the irradiation anti-parallel direction, the first irradiation side direction, and the second irradiation side direction are defined. Even so, the irradiation parallel direction, the irradiation anti-parallel direction, the first irradiation side direction, and the second irradiation side direction are the same as the directions expressed using the projection of the aforementioned electron beam probe EP. When defining the irradiation parallel direction, the irradiation anti-parallel direction, the first irradiation side direction, and the second irradiation side direction in this way, if the EBSD detector 120 is not parallel to the electron beam probe EP, it is assumed that the inclination angle of the EBSD detector 120 with respect to the electron beam probe EP is changed so as to be parallel to the electron beam probe EP. As described above, the irradiation parallel direction, the irradiation anti-parallel direction, the first irradiation side direction, and the second irradiation side direction are determined.

[0021] Also, the irradiation direction of the electron beam probe EB is not limited to vertically downward. The irradiation parallel direction, the irradiation anti-parallel direction, the first irradiation side direction, and the second irradiation side direction are respectively determined according to the aforementioned definitions according to the irradiation direction of the electron beam probe EB.

[0022] In the following description, for the sake of simplicity of notation, when the electron beam probe EP is projected onto the surface of the sample S, the direction parallel to the irradiation direction of the projected electron beam probe EP is referred to as the -Y direction. That is, the -Y direction is, for example, the direction in which the orthographic projection vector obtained by orthographically projecting the electron beam probe EP onto the surface of the sample S, regarding the vector in the traveling direction of the electron beam probe EP as a reference vector, points. Also, the direction opposite to the irradiation parallel direction on the surface of the sample S is referred to as the +Y direction. Also, of the two directions perpendicular to each other and opposite to each other in the irradiation parallel direction on the surface of the sample S, the leftward and rightward directions when looking at the surface of the sample S from the side of the EBSD detector 120 with the +Y direction as the top are referred to as the -X direction and the +X direction, respectively.

[0023] In the example shown in FIG. 1, the upward direction corresponds to the +Y direction, the downward direction corresponds to the -Y direction, the rightward direction is the +X direction, and the leftward direction is the -X direction. Note that the upward direction corresponding to the +Y direction means that the upward direction becomes the +Y direction when the sample S and the EBSD detector 120 are arranged in parallel, and the downward direction corresponding to the -Y direction means that the downward direction becomes the -Y direction when the sample S and the EBSD detector 120 are arranged in parallel. Also, assuming that the surface of the sample S is in a state parallel to the electron beam probe EP, even when expressing the ±X directions and the ±Y directions with the direction parallel to the irradiation direction of the electron beam probe EP on the surface of the sample S as the -Y direction, the ±X directions and the ±Y directions are the same as the directions expressed using the projection of the electron beam probe EP described above.

[0024] As described above, by previously measuring the crystal orientation of the sample S to be observed using the EBSD method or the Laue method using X-rays, the direction of the main axis of the crystal of the sample S can be easily specified. In the present embodiment, the

[0100] and [-100] directions of the sample S are made to correspond to the +X direction and -X direction on the surface of the sample S, respectively, and the

[0010] and [0-10] directions of the sample S are made to correspond to the +Y direction and -Y direction on the surface of the sample S, respectively. It is preferable to suppress the deviation angle between the

[0100] and

[0010] directions and the +X direction and +Y direction of the sample S to about ±5°. In this way, not only the directions of the crystal axes of the sample S (

[0100] , [-100],

[0010] , [0-10] directions) are completely parallel to the ±X directions and ±Y directions, but such deviations are also allowed. The fact that the directions of the crystal axes of the sample S (

[0100] , [-100],

[0010] , [0-10] directions) correspond to the ±X directions and ±Y directions means that not only the directions of the crystal axes of the sample S are completely parallel to the ±X directions and ±Y directions, but such deviations may also be allowed. Note that the

[0100] and [-100] directions of the sample S may be made to correspond to the -X direction and +X direction on the surface of the sample S, respectively, and the

[0010] and [0-10] directions may be made to correspond to the -Y direction and +Y direction on the surface of the sample S, respectively. Further, the

[0100] and [-100] directions may be made to correspond to either the -Y direction or +Y direction on the surface of the sample S, and the

[0010] and [0-10] directions may be made to correspond to either the -X direction or +X direction on the surface of the sample S, respectively.

[0025] As described above, the electron beam probe EP is focused and scanned on the sample S set in the sample holder 112. The optical system in the scanning electron microscope is composed of an electron gun, a focusing lens, a scanning deflector, etc., and it may be any one installed in a commercially available known scanning electron microscope and is not particularly limited.

[0026] When the electron beam probe EB irradiates a measurement point of the inclined sample S, the backscattered electrons BE that jump out from the surface of the sample S toward the EBSD detector 120 reach the EBSD detector 120. The EBSD detector 120 includes, for example, a fluorescent screen as a detection surface for backscattered electrons. When the backscattered electrons that reach the EBSD detector 120 hit the EBSD detector 120 (fluorescent screen), light is generated. The generated light reaches an imaging device (for example, a CCD (Charge Coupled Device) detector or a CMOS (Complementary MOS) detector) through a condenser lens in the imaging device 130 and is converted into an electrical signal. The electrical signal is stored as an EBSD image, which is an image showing the diffraction pattern of the backscattered electrons that reach the EBSD detector 120, at a resolution defined by the number of pixels of the imaging device. The EBSD image has the normalized electrical signal intensity per pixel as a pixel value. For example, when the pixel value of each pixel is stored as 8-bit data, the pixel value is represented as a luminance value with 256 gradations. Note that the scanning electron microscope 110, the EBSD detector 120, and the imaging device 130 themselves may be realized by known ones and are not limited to the above-described configurations.

[0027] The information processing device 140 is a device that executes information processing for acquiring information regarding the crystal orientation and the magnetic domain structure (the size, shape, and magnetization direction of each magnetic domain) in the sample S of the steel sheet based on the EBSD image. The information processing device 140 includes, as its functions, an image acquisition unit 141, a crystal orientation acquisition unit 142, a first backscattered electron image creation unit 143, a second backscattered electron image creation unit 144, and a magnetic domain structure acquisition unit 145. Note that the hardware of the information processing device 140 is not particularly limited and is realized, for example, by a computer including a central processing unit, a main storage device, an auxiliary storage device, an input device, and an output device. FIG. 3 is a diagram showing an example of an outline of the processing in the information processing device 140.

[0028] The image acquisition unit 141 acquires an EBSD image 310 as shown in FIG. 3 (EBSD image acquisition step in step S203). As shown in FIG. 3, in the present embodiment, a case where the image acquisition unit 141 acquires an EBSD image 310 at each of a plurality of measurement points MP set in the observation region of the sample S is exemplified. In the present embodiment, it is assumed that the observation region of the crystal orientation of the sample S and the observation region of the magnetic domain structure of the sample S are the same, and the measurement points MP for observing the crystal orientation of the sample S and the measurement points MP for observing the magnetic domain structure of the sample S are the same. However, the measurement points for observing the crystal orientation of the sample S and the measurement points for observing the magnetic domain structure of the sample S may be different. For example, the magnetic domain structure of the sample S may be made wider than the observation region of the crystal orientation observation region of the sample S, or the number of measurement points for observing the magnetic domain structure of the sample S may be made larger than the number of measurement points for observing the crystal orientation of the sample S.

[0029] The crystal orientation acquisition unit 142 acquires information indicating the crystal orientation in the sample S based on the EBSD image 310 at each measurement point MP of the sample S (crystal orientation acquisition step in step S204). In FIG. 3, a case where the information indicating the crystal orientation in the sample S is the crystal orientation map 320 is exemplified. The crystal orientation map 320 is an image created by storing, for each measurement point MP, a pixel value (color) corresponding to the crystal orientation calculated from the EBSD image 310 obtained by irradiating the measurement point MP of the sample S with the electron beam probe EP in the region (pixel) 321 corresponding to the measurement point MP. The analysis of the crystal orientation is realized by EBSD analysis (for example, analysis of the position of Kikuchi bands, etc.) and is realized by a known technique, so the detailed description thereof is omitted here. Further, the information processing device 140 may acquire, for example, the residual stress (residual strain) in the sample S based on the image shift between a plurality of EBSD images 310 at each measurement point MP in the sample S. The method for analyzing the residual stress (residual strain) in the sample S is also realized by a known technique, so the detailed description thereof is omitted here.

[0030] The first backscattered electron image creation unit 143 creates a backscattered electron image 330 based on the EBSD image 310 at each measurement point MP of the sample S (the first backscattered electron image creation step in step S205 of FIG. 2). The backscattered electron image 330 stores, in a region (pixel) 331 corresponding to the measurement point MP, pixel values indicating the intensity of backscattered electrons calculated from the EBSD image 310 obtained by irradiating the measurement point MP of the sample S with an electron beam probe EP. The backscattered electron image 330 is an image created by performing this operation for each measurement point MP. As described above, the EBSD image 310 stores the electrical signal intensity normalized for each pixel as a pixel value. Therefore, by integrating the pixel values, it is possible to calculate a value proportional to the number of backscattered electrons (the intensity of backscattered electrons) that reached the EBSD detector 120. Therefore, in the present embodiment, a case where the number of backscattered electrons (the intensity of backscattered electrons) is represented by the integrated value of the pixel values of the EBSD image 310 is illustrated.

[0031] However, in the present embodiment, the first backscattered electron image creation unit 143 creates a backscattered electron image by calculating the integrated value of pixel values in a partial region of the region of the EBSD image 310 without calculating the integrated value of pixel values in all regions of the EBSD image 310. Specifically, in the present embodiment, the first backscattered electron image creation unit 143 integrates the pixel values in the region above the position corresponding to the measurement point MP to create an upper backscattered electron image as an example of a backscattered electron image on the anti-parallel irradiation direction side, integrates the pixel values in the region below the position corresponding to the measurement point MP to create a lower backscattered electron image as an example of a backscattered electron image on the parallel irradiation direction side, integrates the pixel values in the region to the left of the position corresponding to the measurement point MP to create a left backscattered electron image as an example of a first irradiation side direction backscattered electron image, and integrates the pixel values in the region to the right of the position corresponding to the measurement point MP to create a backscattered electron image including a right backscattered electron image as an example of a second irradiation side direction backscattered electron image. However, as will be described later, the first backscattered electron image creation unit 143 may create only at least one of the upper backscattered electron image and the lower backscattered electron image. Here, the position in the region of the EBSD image 310 corresponding to the measurement point MP is the coordinate position in the EBSD image 310 corresponding to the foot of the perpendicular dropped from the intersection point (measurement point MP) of the electron beam probe EP and the sample S to the EBSD detector 120. In the example shown in FIG. 1, the coordinate positions in the up, down, left, and right directions of the measurement point MP are the same as the coordinate positions in the up, down, left, and right directions of the EBSD detector 120.

[0032] The upper backscattered electron image is obtained by calculating the intensity of backscattered electrons in at least a partial region above the position corresponding to the measurement point MP in the region of the EBSD image 310 while varying the measurement point MP. In the present embodiment, the case where the position corresponding to the measurement point MP is the center of the EBSD image 310 is exemplified. Therefore, the upper backscattered electron image is an image in which the integrated value of at least a part of the pixel values in the upper half of the EBSD image 310 obtained by irradiating the measurement point MP with the electron beam probe EP is stored in the region (pixel) 331 corresponding to the measurement point MP.

[0033] The left-side reflected electron image is obtained by calculating the intensity of reflected electrons in at least a partial region on the left side of the position corresponding to the measurement point MP in the region of the EBSD image 310, and performing this calculation while varying the measurement point MP. Specifically, the left-side reflected electron image is an image in which the integrated value of pixel values of at least a partial region in the left half of the EBSD image 310 obtained by irradiating the measurement point MP with the electron beam probe EP is stored in the region (pixel) 331 corresponding to the measurement point MP.

[0034] The right-side reflected electron image is obtained by calculating the intensity of reflected electrons in at least a partial region on the right side of the position corresponding to the measurement point MP in the region of the EBSD image 310, and performing this calculation while varying the measurement point MP. Specifically, the right-side reflected electron image is an image in which the integrated value of pixel values of at least a partial region in the right half of the EBSD image 310 obtained by irradiating the measurement point MP with the electron beam probe EP is stored in the region (pixel) 331 corresponding to the measurement point MP.

[0035] The bottom-side reflected electron image is obtained by calculating the intensity of reflected electrons in at least a partial region on the bottom side of the position corresponding to the measurement point MP in the region of the EBSD image 310, and performing this calculation while varying the measurement point MP. Specifically, the bottom-side reflected electron image is an image in which the integrated value of pixel values of at least a partial region in the bottom half of the EBSD image 310 obtained by irradiating the measurement point MP with the electron beam probe EP is stored in the region (pixel) 331 corresponding to the measurement point MP.

[0036] Based on the reflected electron images (the top-side reflected electron image, the bottom-side reflected electron image, the left-side reflected electron image, and the right-side reflected electron image) created by the first reflected electron image creation unit 143, the second reflected electron image creation unit 144 creates a reflected electron image in which the contrast derived from magnetic domains having magnetization directions corresponding to the

[0100] direction and the [-100] direction, or the contrast derived from magnetic domains having magnetization directions corresponding to the

[0010] direction and the [0-10] direction is enhanced (increased), and the contrast derived from the shape (concavity and convexity) of the surface of the sample S is relaxed (reduced) (the second reflected electron image creation step in step S206 of FIG. 2).

[0037] The contrast observed in the reflected electron image includes not only the contrast derived from the magnetic domain structure (magnetic domains and magnetization direction) but also the contrast derived from the shape (concavity and convexity) of the surface of the sample S. For this reason, there is a problem that it is difficult to obtain the contrast derived from the true magnetic domain structure (magnetic domains and magnetization direction). In particular, it becomes a serious problem when quantifying the magnitude of magnetization from the magnitude of the contrast derived from the magnetic domain structure (magnetic domains and magnetization direction). In the following description, the contrast derived from the shape of the surface of the sample S is also referred to as the concavity-convexity contrast. Further, the contrast derived from the magnetic domain structure (magnetic domains and magnetization direction) is also referred to as the magnetic domain contrast.

[0038] In order to prevent the above-described concavity-convexity contrast from being superimposed on the magnetic domain contrast, it is important to make the concavity and convexity formed during the surface finishing of the sample S as small as possible. However, it is very difficult to perform a surface finish without concavity and convexity. Therefore, the inventors considered that if the concavity-convexity contrast in the reflected electron image that inevitably exists can be relaxed, the magnetic domain contrast can be emphasized.

[0039] As a result, the inventors found that the contrast appearing in the upper reflected electron image is mainly represented as the concavity-convexity contrast. For example, the following two reasons are conceivable for this. FIG. 4A is a diagram for explaining that the contrast appearing in the upper reflected electron image is mainly represented as the concavity-convexity contrast. Specifically, FIG. 4A is a diagram conceptually showing the difference in the moving distances in the sample between the reflected electrons traveling upward and the reflected electrons traveling downward.

[0040] Next, the first reason will be explained. The Lorentz force F, which is the force acting on a charge q (here an electron) moving with a velocity v in a space where a magnetic field with magnetic flux density B exists, is represented by F = qvBsinθ. θ is the angle formed by the vector of the magnetic flux density B and the vector of the velocity v. To increase the magnetic domain contrast, it is necessary to increase the Lorentz force F so that the electron trajectory changes significantly under the influence of the magnetic field in the sample S. In the present embodiment, since the case where the electron beam probe EP is directed downward is illustrated, as shown in FIG. 4A, the moving distance in the sample S of the reflected electrons traveling from the inclined sample S toward the surface of the sample S is shorter for the distance DU when moving upward than for the distance DD when moving downward. For this reason, the distance over which the reflected electrons BE are subjected to the Lorentz force F is smaller when moving upward than when moving downward. For this reason, in the upper reflected electron image, the magnetic domain contrast is likely to be relaxed. Also, in the surface region of the sample S without unevenness, the lower reflected electron image is more likely to be brighter than the upper reflected electron image. This is due to the fact that since the electron beam probe EP is directed downward, the generation direction of the reflected electrons is likely to be downward.

[0041] If the velocity of the incident electrons incident on the sample S is mentioned, the Lorentz force F received by the incident electrons and the reflected electrons can be increased. Therefore, in the EBSD image acquisition step of step S203 in FIG. 2, it is preferable that the acceleration voltage of the electron gun is high. For example, it is preferable to set the acceleration voltage of the electron gun to 20 kV or more. This is because when the acceleration voltage of the electron gun is less than 20 kV, the Lorentz force F received by the reflected electrons is small, and magnetic domain contrast may not easily occur in the reflected electron image appearing on the EBSD detector 120.

[0042] As a second reason, in the present embodiment, since the case where the electron beam probe EP is directed downward is illustrated, the energy of the reflected electrons moving upward is smaller than the energy of the reflected electrons moving downward. For this reason, in the upper reflected electron image, the magnetic domain contrast is likely to be relaxed.

[0043] From the above, it is considered that the contrast appearing in the upper backscattered electron image is dominated by the uneven contrast rather than the magnetic domain contrast, and the contrast appearing in the upper backscattered electron image can be regarded as the contrast in which the shape of the surface of the sample S is emphasized.

[0044] In addition, the present inventors have found that the uneven contrast is reversed between the upper backscattered electron image and the lower backscattered electron image. The reason will be described with reference to FIG. 4B. FIG. 4B is a diagram for explaining that the uneven contrast is reversed between the side backscattered electron image and the lower backscattered electron image. Specifically, FIG. 4B is a diagram conceptually showing that the number of backscattered electrons traveling downward due to the unevenness of the surface of the sample S decreases. In FIG. 4B, when the backscattered electrons traveling upward from the illustrated generation point of the backscattered electrons reach a position above the generation point in the region of the EBSD detector 120, there is nothing to block the backscattered electrons and they are observed brightly. On the other hand, when the backscattered electrons traveling downward from the illustrated generation point of the backscattered electrons reach a position below the generation point in the region of the EBSD detector 120, they are blocked by the convex portion and observed darkly. Therefore, it is considered that the lower backscattered electron image becomes dark at the position where the upper backscattered electron image becomes bright (the pixel value is large), and the lower backscattered electron image becomes bright at the position where the upper backscattered electron image becomes dark.

[0045] From the above, the present inventors have found that by using at least one of the upper backscattered electron image and the lower backscattered electron image, the contrast derived from the shape (unevenness) generated in the ±Y direction on the surface of the sample S can be extracted as the uneven contrast. Hereinafter, a specific example of a method for the second backscattered electron image creation unit 144 to extract the contrast derived from the magnetic domain having the magnetization direction corresponding to the

[0100] direction and the [-100] direction, and the contrast derived from the magnetic domain having the magnetization direction corresponding to the

[0010] direction and the [0-10] direction using the upper backscattered electron image, the lower backscattered electron image, the left backscattered electron image, and the right backscattered electron image will be described.

[0046] First, consider the influence of the internal magnetic field of the sample S on the trajectory of the backscattered electrons that jump out from the surface of the sample S toward the EBSD detector 120 when the electron beam probe EP irradiates the inclined sample S. FIG. 5 conceptually illustrates an example of the behavior of the backscattered electrons BE when the measurement point MP is in a magnetic domain with the magnetization direction in the +X direction (the direction corresponding to the

[0100] direction) and the -X direction (the direction corresponding to the [-100] direction). FIG. 6 conceptually illustrates an example of the behavior of the backscattered electrons BE when the measurement point MP is in a magnetic domain with the magnetization direction in the +Y direction (the direction corresponding to the

[0010] direction) and the -Y direction (the direction corresponding to the [0-10] direction).

[0047] In FIG. 5(a), when the internal magnetic field of the sample S is magnetized in the +X direction, the backscattered electrons BE heading toward the EBSD detector 120 receive a downward Lorentz force F inside the sample S. Therefore, the arrival position 511 of the backscattered electrons BE at the detector 120 is shifted downward from the arrival position 510 when there is no internal magnetic field. Conversely, as shown in FIG. 5(b), when the internal magnetic field of the sample S is magnetized in the -X direction, the backscattered electrons BE heading toward the EBSD detector 120 receive an upward Lorentz force F inside the sample S. Therefore, the arrival position 512 of the backscattered electrons BE at the detector 120 is shifted upward from the arrival position 510 when there is no internal magnetic field. In this case, if a backscattered electron image is created only with the backscattered electrons BE that reach above the center of the EBSD detector 120, a magnetic domain with the magnetization direction in the -X direction will be observed brightly. However, for the reasons described above, in such a backscattered electron image, the magnetic domain contrast in the magnetization direction of the -X direction is relaxed, and the uneven contrast is emphasized. On the other hand, if a backscattered electron image is created only with the backscattered electrons BE that reach below the center of the EBSD detector 120, a magnetic domain with the magnetization direction in the +X direction will be observed brightly.

[0048] Similarly, when creating a backscattered electron image using only the backscattered electrons BE that reach the right side of the center of the EBSD detector 120, magnetic domains with the magnetization direction in the +Y direction in the sample S are clearly observed (see the arrival position 510 of the backscattered electrons BE when there is no internal magnetic field shown in FIG. 6(a) and the arrival position 611 of the backscattered electrons BE when the internal magnetic field is magnetized in the +Y direction). Further, when creating a backscattered electron image using only the backscattered electrons BE that reach the left side of the center of the EBSD detector 120, magnetic domains with the magnetization direction in the -Y direction in the sample S are clearly observed (see the arrival position 510 of the backscattered electrons BE when there is no internal magnetic field shown in FIG. 6(b) and the arrival position 612 of the backscattered electrons BE when the internal magnetic field is magnetized in the -Y direction).

[0049] As described above, in the present embodiment, the

[0100] , [-100] directions of the sample S are made to correspond to the +X direction and -X direction on the surface of the sample S, respectively. Therefore, for example, when creating a reflected electron image (lower reflected electron image) with the reflected electron BE that reaches below the center of the EBSD detector 120, the region that is most brightly observed corresponds to the magnetic domain having the magnetization direction in the +X direction (i.e., the direction corresponding to the

[0100] direction), and the region that is most darkly observed corresponds to the magnetic domain having the magnetization direction in the -X direction (i.e., the direction corresponding to the [-100] direction). Furthermore, when creating a reflected electron image (lower reflected electron image) with the reflected electron BE that reaches below the center of the EBSD detector 120, the uneven contrast is reversed compared to the case of creating a reflected electron image (upper reflected electron image) with the reflected electron BE that reaches above the center of the EBSD detector 120. For this reason, when creating a reflected electron image (lower reflected electron image) with the reflected electron BE that reaches below the center of the EBSD detector 120, the uneven contrast is superimposed on the magnetic domain contrast in the magnetization directions of the ±X directions. Also, the

[0010] , [0-10] directions of the sample S are made to correspond to the +Y direction and -Y direction on the surface of the sample S, respectively. Therefore, for example, when creating a reflected electron image (left reflected electron image) with the reflected electron BE that reaches to the left of the center of the EBSD detector 120, the region that is most brightly observed corresponds to the magnetic domain having the magnetization direction in the -Y direction (i.e., the direction corresponding to the [0-10] direction), and the region that is most darkly observed corresponds to the magnetic domain having the magnetization direction in the +Y direction (i.e., the direction corresponding to the

[0010] direction).

[0050] As described above, when creating a reflected electron image using the reflected electron BE that reaches below, to the left, and to the right of the center of the EBSD detector 120, respectively, a magnetic domain having a specific magnetization direction can be brightly (or darkly) displayed, and the contrast of the magnetic domain in the magnetization direction can be emphasized. Also, when creating a reflected electron image using the reflected electron BE that reaches above the center of the EBSD detector 120, the uneven contrast can be emphasized.

[0051] At this time, when a region near the edge of the EBSD detector 120 is selected, magnetic domain contrast and unevenness contrast are likely to be enhanced. This is because when the electron orbit changes due to the Lorentz force F, the change in the arrival position on the EBSD detector 120 of the electrons heading toward the edge of the EBSD detector 120 appears larger than that of the electrons heading toward the center of the EBSD detector 120. In a normal EBSD measurement setup, it is preferable to integrate the pixel values of a region corresponding to an area of 1 / 20 or more of the area of the detection region of the reflected electron image of the EBSD detector 120 at each of the upper, lower, left, and right sides of the center of the EBSD image 310. This is because if the integrated area is small, the number of counted pixel values decreases, and sufficient magnetic domain contrast and unevenness contrast may not be obtained. Also, it is preferable not to select a region near the center of the EBSD detector 120. For example, in a region near the center of the EBSD detector 120, the influence of magnetic domains in the +X direction, -X direction, +Y direction, and -Y direction may be significantly mixed. For example, a divided region is set by dividing the EBSD image 310 into a plurality of regions such that at least three regions exist in each of the vertical and horizontal directions, and the upper reflected electron image, the lower reflected electron image, the left reflected electron image, and the right reflected electron image are each created using the pixel values of the divided region 310 closest to the edge of the EBSD image without using the pixel values of the divided region closest to the center of the EBSD image 301. The number of divisions of the EBSD image 310 is not limited to this, and for example, it may be divided into four in the vertical and horizontal directions.

[0052] Also, for example, when the EBSD detector 120 is divided into four divided regions that are divided into four parts vertically and horizontally, in the upper left divided region and the lower left divided region, in addition to the magnetic domains in the -X direction and +X directions, the magnetic domains in the -Y direction also become brighter. Further, in the lower left divided region and the lower right divided region of the reflected electron image, in addition to the magnetic domains in the -Y direction and +Y directions, the magnetic domains in the +X direction also become brighter. Therefore, simply adding the pixel values of the EBSD image 310 for each of the regions above, below, to the left, and to the right of the center of the EBSD image 310 (simply creating the upper reflected electron image, the lower reflected electron image, the left reflected electron image, and the right reflected electron image) does not easily allow for accurately extracting the magnetic domain structure (magnetic domains and magnetic domain directions).

[0053] Therefore, in the present embodiment, the second reflected electron image creation unit 144 executes subtracting the pixel value of the left reflected electron image from the pixel value of the right reflected electron image. Further, the second reflected electron image creation unit 144 executes either adding the pixel value of the upper reflected electron image to the pixel value of the lower reflected electron image or subtracting the pixel value of the upper reflected electron image from the added value of the pixel value of the left reflected electron image and the pixel value of the right reflected electron image. Note that the addition and subtraction of the pixel values are executed at the same pixel positions. The reason for executing such calculations will be described below.

[0054] As described with reference to FIG. 4B, at the measurement point MP where the uneven contrast occurs, when the upper reflected electron image is bright (when the pixel value is large), the lower reflected electron image is dark, and when the upper reflected electron image is dark, the lower reflected electron image is bright. From this, the inventors have found that when adding the pixel value of the upper reflected electron image to the pixel value of the lower reflected electron image, the uneven contrast is alleviated and the magnetic domain contrast in the ±X directions is emphasized.

[0055] FIG. 7 conceptually shows an example of the change in contrast by adding the pixel value of the upper backscattered electron image and the pixel value of the lower backscattered electron image. Here, for simplicity of explanation, it is assumed that in the magnetic domain magnetized in the -X direction, only the pixel value due to unevenness appears in the backscattered electron image. Also, in the magnetic domain magnetized in the +X direction, only the pixel value due to magnetization in the +X direction and the pixel value due to unevenness appear. Further, the pixel value due to magnetization in the +X direction is set to 10, and the pixel value due to unevenness is set to 1.

[0056] As shown in FIG. 7(a), when an uneven contrast occurs in which the magnetic domain 701 magnetized in the -X direction has a larger pixel value than the magnetic domain 702 magnetized in the +X direction adjacent to the magnetic domain 701, the pixel value of the upper backscattered electron image in the magnetic domain 701 becomes 1, and the pixel value of the upper backscattered electron image in the magnetic domain 702 becomes 0. When only the unevenness on the surface of the sample S is considered, if the upper backscattered electron image in the magnetic domain 701 is bright, the lower backscattered electron image in the magnetic domain 701 becomes dark. Therefore, the pixel value of the lower backscattered electron image in the magnetic domain 701 becomes 0. On the contrary, when only the unevenness on the surface of the sample S is considered, if the upper backscattered electron image in the magnetic domain 702 is dark, the lower backscattered electron image in the magnetic domain 702 becomes bright. Therefore, the pixel value of the lower backscattered electron image in the magnetic domain 702 is a value (=11) obtained by adding the pixel value (=10) due to magnetization in the +X direction and the pixel value (=1) due to unevenness. Thus, by adding the pixel value of the upper backscattered electron image and the pixel value of the lower backscattered electron image, the uneven contrast included in the lower backscattered electron image can be relaxed, and the original domain contrast (=10(=11 - 1)) in the ±X direction can be obtained, and the domain contrast in the ±X direction is emphasized.

[0057] Also, as shown in FIG. 7(b), when there is an uneven contrast such that the pixel value of the magnetic domain 702 magnetized in the +X direction is larger than that of the magnetic domain 701 magnetized in the -X direction, the pixel value of the upper backscattered electron image in the magnetic domain 702 becomes 1, and the pixel value of the upper backscattered electron image in the magnetic domain 701 becomes 0. When only considering the unevenness on the surface of the sample S, if the upper backscattered electron image in the magnetic domain 701 is dark, the lower backscattered electron image in the magnetic domain 701 becomes bright. Therefore, the pixel value of the lower backscattered electron image in the magnetic domain 701 becomes 1. Conversely, when only considering the unevenness on the surface of the sample S, if the upper backscattered electron image in the magnetic domain 702 is bright, the lower backscattered electron image in the magnetic domain 702 becomes dark. Therefore, the pixel value of the lower backscattered electron image in the magnetic domain 702 becomes only the pixel value (=10) resulting from being magnetized in the +X direction. Thus, by adding the pixel value of the upper backscattered electron image and the pixel value of the lower backscattered electron image, the uneven contrast included in the lower backscattered electron image can be alleviated, and the original magnetic domain contrast (=10(=11 - 1)) in the ±X direction can be obtained, and the magnetic domain contrast in the ±X direction is emphasized. In the present embodiment, by adding the pixel value of the upper backscattered electron image and the pixel value of the lower backscattered electron image, a backscattered electron image in which the magnetic domain contrast in the ±X direction is emphasized and the uneven contrast is alleviated is created as an example of the first irradiation direction magnetic domain contrast enhanced image. In the following description, the backscattered electron image is also referred to as the first X-direction magnetic domain contrast enhanced image.

[0058] Further, the inventors have found that by subtracting the pixel value of the left backscattered electron image from the pixel value of the right backscattered electron image, the magnetic domain contrast in the ±Y direction can be emphasized and the uneven contrast can be alleviated.

[0059] FIG. 8 conceptually shows an example of the change in contrast by subtracting the pixel value of the left-side reflected electron image from the pixel value of the right-side reflected electron image. Here, for simplicity of explanation, in the magnetic domain magnetized in the +Y direction, it is assumed that only the pixel value due to magnetization in the +Y direction and the pixel value due to unevenness appear, and in the magnetic domain magnetized in the -Y direction, only the pixel value due to magnetization in the -Y direction and the pixel value due to unevenness appear. Also, the pixel value due to magnetization in the ±Y direction is set to 10 each, and the pixel value due to unevenness is set to 1.

[0060] As shown in FIG. 8(a), when there is no uneven contrast between the magnetic domain 801 magnetized in the -Y direction and the magnetic domain 802 magnetized in the +Y direction adjacent to the magnetic domain 801, subtracting the pixel value of the right-side reflected electron image from the pixel value of the left-side reflected electron image results in the magnetic domain contrast in the ±Y direction changing from 10 to 20 (=10 - (-10)), and the magnetic domain contrast in the ±Y direction can be emphasized.

[0061] As shown in FIG. 8(b), when an uneven contrast occurs where the pixel value of the magnetic domain 801 magnetized in the -Y direction is larger than that of the magnetic domain 802 magnetized in the +Y direction, the pixel value due to unevenness is larger for the magnetic domain 801 in both the left-side reflected electron image and the right-side reflected electron image. Therefore, the pixel values of the left-side reflected electron image and the right-side reflected electron image in the magnetic domain 801 are 11 and 1, respectively. Thus, subtracting the pixel value of the right-side reflected electron image from the pixel value of the left-side reflected electron image results in the magnetic domain contrast in the ±Y direction changing from 10 to 20 (=10 - (-10)), which is the same value as the magnetic domain contrast in the ±Y direction in the case without the uneven contrast shown in FIG. 8(a). In this way, the magnetic domain contrast in the ±Y direction can be emphasized and the uneven contrast can be alleviated.

[0062] As shown in FIG. 8(c), when there is an uneven contrast in which the pixel value of the magnetic domain 802 magnetized in the +Y direction is larger than that of the magnetic domain 801 magnetized in the -Y direction, the pixel value derived from the unevenness is larger for the magnetic domain 802 in both the left-side reflected electron image and the right-side reflected electron image. Therefore, the pixel values of the left-side reflected electron image and the right-side reflected electron image in the magnetic domain 802 are 1 and 11, respectively. Thus, when the pixel value of the right-side reflected electron image is subtracted from the pixel value of the left-side reflected electron image, the magnetic domain contrast in the ±Y direction becomes 10 to 20 (= 10 - (-10)), which is the same value as the magnetic domain contrast in the ±Y direction when there is no uneven contrast shown in FIG. 8(a). In this way, the magnetic domain contrast in the ±Y direction can be emphasized and the uneven contrast can be alleviated. In the following description, by subtracting the pixel value of the upper-side reflected electron image from the pixel value of the lower-side reflected electron image, a reflected electron image in which the magnetic domain contrast in the ±Y direction is emphasized and the uneven contrast is alleviated is created as an example of an irradiation-side direction magnetic domain contrast emphasized image. In the following description, the reflected electron image is also referred to as a Y-direction magnetic domain contrast emphasized image. Note that the subtraction of the pixel value of the upper-side reflected electron image from the pixel value of the lower-side reflected electron image may be realized by subtracting the pixel value of the lower-side reflected electron image from the pixel value of the upper-side reflected electron image, or may be realized by subtracting the pixel value of the lower-side reflected electron image from the pixel value of the lower-side reflected electron image. Further, since it is only necessary to know the contrast (difference in pixel values (luminance values)) of the image, if the result of the subtraction becomes a negative value, the pixel value after the subtraction may be normalized (for example, expressed as a relative value with the minimum value being 0).

[0063] Furthermore, the inventors have found that when adding the pixel value of the left-side reflected electron image and the pixel value of the right-side reflected electron image, the magnetic domain contrast in the ±Y direction is averaged, so that the magnetic domain contrast in the ±X direction is emphasized. For example, in the lower left or lower right region of the EBSD image 310, since the magnetic domain having the magnetization direction in the +X direction is brightly shown and the magnetic domain having the magnetization direction in the -X direction is darkly shown, when adding the pixel value of the left-side reflected electron image and the pixel value of the right-side reflected electron image, the magnetic domain contrast in the ±X direction is emphasized. However, in this case, since the uneven contrast is not relaxed, after adding the pixel value of the left-side reflected electron image and the pixel value of the right-side reflected electron image, the uneven contrast is relaxed by subtracting the pixel value of the upper-side reflected electron image.

[0064] FIG. 9 conceptually shows an example of the change in contrast by subtracting the pixel value of the upper-side reflected electron image after adding the pixel value of the left-side reflected electron image and the pixel value of the right-side reflected electron image. Here, an example is illustrated in which the pixel value resulting from magnetization in the -Y direction is included in the magnetic domain 901 magnetized in the -X direction, and the pixel value resulting from magnetization in the +Y direction is included in the magnetic domain 902 magnetized in the +X direction adjacent to the magnetic domain 901. Further, an example is illustrated in which an uneven contrast occurs in which the magnetic domain 901 magnetized in the -X direction has a larger pixel value than the magnetic domain 902. Also, the pixel value resulting from magnetization in the +X direction is set to 7, the pixel value resulting from magnetization in the ±Y direction is set to 3 each, and the pixel value resulting from unevenness is set to 1.

[0065] As shown in FIG. 9(a), when only extracting the pixel values resulting from magnetization in the ±Y direction included in the magnetic domains 901 and 902 and adding the pixel value of the left-side reflected electron image and the pixel value of the right-side reflected electron image, the magnetic domain contrast in the ±Y direction is relaxed from 3 (=3 - 0) to 0 (=3 - 3).

[0066] As shown in FIG. 9(b), only the pixel values resulting from magnetization in the ±X direction included in magnetic domains 901 and 902 are extracted, and the pixel values of the left-side reflected electron image and the pixel values of the right-side reflected electron image are added. Then, the magnetic domain contrast in the ±X direction becomes from 6 (=7 - 1) to 12 (=14 - 2), and the magnetic domain contrast in the ±X direction is enhanced. Then, as shown in FIG. 9(c), when the pixel values of the upper-side reflected electron image are subtracted from the pixel values added in this way, the magnetic domain contrast in the ±X direction becomes from 12 to 13 (=14 - 1), and the uneven contrast (=1) can be mitigated. In this embodiment, by adding the pixel value of the left-side reflected electron image and the pixel value of the right-side reflected electron image, a reflected electron image is created in which the magnetic domain contrast in the ±Y direction is relaxed and the magnetic domain contrast in the ±X direction is emphasized. In the following description, the reflected electron image is also referred to as a Y-direction magnetic domain contrast relaxation image. Further, in this embodiment, by subtracting the pixel value of the upper-side reflected electron image from the pixel value of the Y-direction magnetic domain contrast relaxation image, a reflected electron image in which the magnetic domain contrast in the ±X direction is emphasized and the unevenness contrast is relaxed is created as an example of a second irradiation direction magnetic domain contrast enhancement image. In the following description, the reflected electron image is also referred to as a second X-direction magnetic domain contrast enhancement image. Note that the second reflected electron image creation unit 144 does not necessarily need to create both the first X-direction magnetic domain contrast enhancement image and the second X-direction magnetic domain contrast enhancement image, and may create only one of them. When creating the first X-direction magnetic domain contrast enhancement image, since the upper-side reflected electron image, the lower-side reflected electron image, the left-side reflected electron image, and the right-side reflected electron image are required, the first reflected electron image creation unit 143 creates the upper-side reflected electron image, the lower-side reflected electron image, the left-side reflected electron image, and the right-side reflected electron image. On the other hand, when creating the second X-direction magnetic domain contrast enhancement image, since the upper-side reflected electron image, the left-side reflected electron image, and the right-side reflected electron image are required, the first reflected electron image creation unit 143 creates the upper-side reflected electron image, the left-side reflected electron image, and the right-side reflected electron image. In this case, the first reflected electron image creation unit 143 does not need to create the lower-side reflected electron image. In the following description, the first X-direction magnetic domain contrast enhancement image or the second X-direction magnetic domain contrast enhancement image is also referred to as an X-direction magnetic domain contrast enhancement image.

[0067] Before the second backscattered electron image creation unit 144 executes addition and subtraction of pixel values of the upper backscattered electron image, lower backscattered electron image, left backscattered electron image, and right backscattered electron image as described above, background processing for reducing (preferably removing) the background (non-uniform brightness) generated in the upper backscattered electron image, lower backscattered electron image, left backscattered electron image, and right backscattered electron image may be executed. As described above, in the present embodiment, in the sample setting step of step S202, when the surface of the sample S is not parallel to the surface of the sample holder 112, gradation may occur in a specific direction in the backscattered electron image. In such a case, it is preferable that the second backscattered electron image creation unit 144 executes background processing for reducing (preferably removing) the gradation. The second backscattered electron image creation unit 144 executes, for example, a process of obtaining the pixel value (intensity) due to the background from the gradient of the gradation in the direction showing the gradation in the backscattered electron image and subtracting this from the pixel value of the original backscattered electron image. The gradient of the gradation is represented, for example, by the slope of a linear function obtained by linearly approximating the relationship between the pixel position and the pixel value due to the gradation in the direction showing the gradation.

[0068] Returning to the descriptions of FIGS. 1 and 2, the magnetic domain structure acquisition unit 145 uses the contrast derived from the magnetic domains having magnetization directions corresponding to the

[0100] direction and the [-100] direction, and the contrast derived from the magnetic domains having magnetization directions corresponding to the

[0010] direction and the [0-10] direction, to acquire information indicating the size, shape, and magnetization direction of each magnetic domain in the sample S (magnetic domain structure acquisition step of step S207 in FIG. 2). Here, the information indicating the size, shape, and magnetization direction of each magnetic domain in the sample S is information of a region including the observation region of the crystal orientation of the sample, and is, for example, information of the same region as the observation region of the crystal orientation of the sample. The information indicating the size, shape, and magnetization direction of each magnetic domain in the sample S may be, for example, an image with different densities or colors for each magnetization direction. In the following description, this image is also referred to as a magnetic domain structure map. The magnetic domain structure map is preferably made to overlap the crystal orientation map 320. That is, it is preferable that the pixels corresponding to each other in the magnetic domain structure map and the crystal orientation map 320 indicate information of the same magnetic domain.

[0069] The magnetic domain structure acquisition unit 145 may display the X-direction magnetic domain contrast-enhanced image and the Y-direction magnetic domain contrast-enhanced image on a computer display. In this case, the analyst may refer to the X-direction magnetic domain contrast-enhanced image and the Y-direction magnetic domain contrast-enhanced image to identify the magnetic domain structure (the size, shape, and magnetic domain direction of each magnetic domain) of the sample S, and create information indicating the size, shape, and magnetization direction of each magnetic domain in the sample S. In this case, the analyst may input the information indicating the size, shape, and magnetization direction of each magnetic domain in the sample S into the information processing apparatus 140.

[0070] Alternatively, the magnetic domain structure acquisition unit 145 may automatically create information indicating the size, shape, and magnetization direction of each magnetic domain in the sample S based on the X-direction magnetic domain contrast-enhanced image and the Y-direction magnetic domain contrast-enhanced image. For example, the magnetic domain structure acquisition unit 145 may identify the magnetic domain direction at each pixel based on the result of comparing the pixel value of each pixel in the X-direction magnetic domain contrast-enhanced image with a threshold value and the result of comparing the pixel value of each pixel in the Y-direction magnetic domain contrast-enhanced image with a threshold value, and create information indicating the size, shape, and magnetization direction of each magnetic domain in the sample S. The magnetic domain structure acquisition unit 145 may display the created information indicating the size, shape, and magnetization direction of each magnetic domain in the sample S on a computer display.

[0071] When creating the magnetic domain structure map, in addition to the X-direction magnetic domain contrast-enhanced image and the Y-direction magnetic domain contrast-enhanced image, reflected electron images other than these may be considered. For example, at least one of the upper reflected electron image, the lower reflected electron image, the left reflected electron image, and the right reflected electron image may be considered. Also, the full-area reflected electron image may be considered. The full-area reflected electron image is a reflected electron image created by storing the integrated value of all the pixels of the EBSD image 310 obtained by irradiating the electron beam probe EP to the measurement point MP of the sample S in the region (pixels) 331 corresponding to the measurement point MP for each measurement point MP.

[0072] As described above, in this embodiment, a reflected electron image of the sample S is created for at least a part of the regions above, below, left, and right of the center of the EBSD detector 120, and a reflected electron image including at least one of the upper and lower reflected electron images and the left and right reflected electron images is created. Based on each reflected electron image, a reflected electron image in which the magnetic domain contrast in the ±X direction or ±Y direction is emphasized and the uneven contrast is alleviated is created as an X-direction magnetic domain contrast-enhanced image and a Y-direction magnetic domain contrast-enhanced image. The magnetic domain structure of the sample S is obtained using the created X-direction magnetic domain contrast-enhanced image and Y-direction magnetic domain contrast-enhanced image. Therefore, it becomes possible to image a magnetic domain having a specific magnetization direction brightly (or darkly), and furthermore, the magnetic domain contrast can be emphasized while alleviating the uneven contrast by adding or subtracting each reflected electron image. Therefore, high-precision information can be obtained as information regarding the magnetic domain structure (the size and shape of the magnetic domain and the magnetization direction within the magnetic domain) without precisely flattening the surface of the sample S. Also, information on the crystal orientation can be obtained together from the analysis result of the Kikuchi band position in the EBSD image. Therefore, the crystal orientation map and the magnetic domain can be observed in the same region, and information regarding the crystal orientation of the steel plate and information regarding the magnetic domain structure (the size and shape of the magnetic domain and the magnetization direction within the magnetic domain) can be observed in the same field of view.

[0073] (Modification example) In this embodiment, an example is illustrated in which a second X-direction magnetic domain contrast-enhanced image with reduced unevenness contrast and enhanced magnetic domain contrast in the ±X directions is created by subtracting the pixel values of the upper backscattered electron image from the pixel values of the Y-direction magnetic domain contrast-relaxed image. However, as described above, the unevenness contrast tends to be reversed between the upper backscattered electron image and the lower backscattered electron image. Furthermore, in the lower backscattered electron image, the region observed as the brightest corresponds to the magnetic domain having the magnetization direction in the +X direction (i.e., the direction corresponding to the

[0100] direction), and the region observed as the darkest corresponds to the magnetic domain having the magnetization direction in the -X direction (i.e., the direction corresponding to the [-100] direction). Therefore, the lower backscattered electron image includes information on the unevenness of the surface of the sample S in addition to the magnetic domains having the magnetization directions in the ±X directions. Thus, by utilizing this fact, a third X-direction magnetic domain contrast-enhanced image with reduced unevenness contrast and enhanced magnetic domain contrast in the ±X directions may also be created as one of the X-direction magnetic domain contrast-enhanced images by adding the pixel values of the lower backscattered electron image to the pixel values of the Y-direction magnetic domain contrast-relaxed image. Therefore, the second backscattered electron image creation unit 144 may create the third X-direction magnetic domain contrast-enhanced image in addition to or instead of at least one of the first X-direction magnetic domain contrast-enhanced image and the second X-direction magnetic domain contrast-enhanced image. As described above, since the unevenness contrast is reversed between the upper backscattered electron image and the lower backscattered electron image, in the example shown in FIG. 9, the pixel values in the magnetic domains 901 and 902 of the lower backscattered electron image are 0 and 8 (=1 + 7), respectively. Therefore, in the examples shown in FIGS. 9(a) and 9(b), by adding the pixel values (0, 8) in the magnetic domains 901 and 902 of the lower backscattered electron image to the pixel values (2, 14) in the magnetic domains 901 and 902 shown in FIG. 9(b), in the third X-direction magnetic domain contrast-enhanced image, the magnetic domain contrast in the ±X directions becomes 12 to 20 (=22 - 2), and the magnetic domain contrast in the ±X directions can be further enhanced while relaxing the unevenness contrast.When creating such a third X-direction magnetic domain contrast-enhanced image, a lower-side reflected electron image, a left-side reflected electron image, and a right-side reflected electron image are required. Therefore, the first reflected electron image creation unit 143 creates a lower-side reflected electron image, a left-side reflected electron image, and a right-side reflected electron image. In this case, the first reflected electron image creation unit 143 does not have to create an upper-side reflected electron image.

[0074] Also, in the present embodiment, the

[0100] , [-100] directions of the sample S are made to correspond to either the +X direction or the -X direction on the surface of the sample S, and the

[0010] , [0-10] directions of the sample S are made to correspond to either the +Y direction or the -Y direction on the surface of the sample S. The sample S is set in the sample holder 112 so that an X-direction magnetic domain contrast-enhanced image (at least one of the first to third X-direction magnetic domain contrast-enhanced images) and a Y-direction magnetic domain contrast-enhanced image are created, and a magnetic domain structure map is created as an example. However, as described above, the

[0100] , [-100] directions of the sample S are made to correspond to either the +Y direction or the -Y direction on the surface of the sample S, and the

[0010] , [0-10] directions of the sample S are made to correspond to either the +X direction or the -X direction on the surface of the sample S. The sample S is set in the sample holder 112 (that is, the sample S is rotated by 90° so that the ±X direction and the ±Y direction are interchanged), an X-direction magnetic domain contrast-enhanced image and a Y-direction magnetic domain contrast-enhanced image are created, and a magnetic domain structure map may be created. Also, in each state where the sample S is rotated by 90° so that the ±X direction and the ±Y direction are interchanged in this way, an X-direction magnetic domain contrast-enhanced image and a Y-direction magnetic domain contrast-enhanced image are created, and a magnetic domain structure map may be created using these X-direction magnetic domain contrast-enhanced images and Y-direction magnetic domain contrast-enhanced images. By doing so, for example, information regarding the magnetic domain structure (the size and shape of the magnetic domains and the magnetization direction within the magnetic domains) can be determined using the X-direction magnetic domain contrast-enhanced images and Y-direction magnetic domain contrast-enhanced images created in each state where the sample S is rotated by 90° so that the ±X direction and the ±Y direction are interchanged. Therefore, the accuracy of the magnetic domain structure map (information regarding the magnetic domain structure) can be further improved.For example, the

[0100] , [-100] direction of the sample S is made to correspond to either the +X direction or the -X direction on the surface of the sample S, and the

[0010] , [0-10] direction of the sample S is made to correspond to either the +Y direction or the -Y direction on the surface of the sample S. Whether the magnetic domain contrast obtained from the X-direction magnetic domain contrast-enhanced image and the Y-direction magnetic domain contrast-enhanced image created by setting the sample S in the sample holder 112 is appropriate or not can be confirmed using the X-direction magnetic domain contrast-enhanced image and the Y-direction magnetic domain contrast-enhanced image created by setting the sample S in the sample holder 112 such that the

[0100] , [-100] direction of the sample S corresponds to either the +Y direction or the -Y direction on the surface of the sample S, and the

[0010] , [0-10] direction of the sample S corresponds to either the +X direction or the -X direction on the surface of the sample S, respectively.

Example

[0075] Next, examples will be described. Note that the present invention is not limited to the following examples. A commercially available Fe-3 mass% Si alloy was used as a sample, and after electrolytic polishing the surface, the crystal orientation was measured using an EBSD device in a scanning electron microscope. Thereafter, the sample was cut so that the surface was parallel to the (001) plane of the BCC structure, and the sample surface was finished by electrolytic polishing to remove the surface processing strain. Further, the sample was attached to a sample holder (EBSD holder) such that the +X direction was parallel to the

[0100] direction and the +Y direction was parallel to the

[0010] direction in the EBSD measurement setup of FIG. 1.

[0076] The sample holder was inserted into the scanning electron microscope and tilted by 70°. The acceleration voltage of the electron gun of the scanning electron microscope was set to 25 kV. The focused electron beam probe was irradiated onto the sample and scanned to obtain an EBSD image for each measurement point. The EBSD image was saved as digital information together with the position information of the measurement point. The resolution of the EBSD image was set to 100 pixels × 100 pixels. Also, the EBSD image was saved in 8 bits. In order to calculate the crystal orientation information (Euler angles) from the EBSD image, commercially available EBSD analysis software (OIM Data Collection 7 manufactured by EDAX) was used.

[0077] Fig. 10 shows an example of the crystal orientation map 1000 obtained by EBSD analysis. As described above, the crystal orientation map 1000 is a color mapping of the orientation of the crystal plane parallel to the sample surface. For convenience of notation, in Fig. 10, it is grayscale, but the crystal orientation map 1000 shown in Fig. 10 is a single red color. Therefore, it can be seen that the observation region of the crystal orientation of the sample is a single crystal and the surface is almost parallel to the (001) plane.

[0078] As shown in FIG. 11, a 100 pixel × 100 pixel EBSD image was divided into 25 divided regions by equally dividing it into five parts in the vertical and horizontal directions on a computer, and the pixel values (pixel intensities) of the pixels in each region were integrated. In the EBSD image divided into 25 divided regions, the three divided regions in the central part at the upper, lower, left, and right ends were selected, the pixel intensities in these three-region areas were calculated, and these were arranged for each measurement point to form a backscattered electron image. FIG. 11(a) shows the divided region selected when creating the upper backscattered electron image, FIG. 11(b) shows the divided region selected when creating the lower backscattered electron image, FIG. 11(c) shows the divided region selected when creating the left backscattered electron image, and FIG. 11(d) shows the divided region selected when creating the right backscattered electron image. In FIGS. 11(a) to 11(d), it is shown that the three thickly shown divided regions are the selected divided regions. Divided regions were also set in the EBSD image so as to correspond to the divided regions of the EBSD detector, and for each measurement point of the sample, the integrated value of the pixel values of the three divided regions of the EBSD image corresponding to the three thickly shown divided regions in FIGS. 11(a) to 11(d) was stored as the pixel value of the measurement point, thereby creating an upper backscattered electron image, a lower backscattered electron image, a left backscattered electron image, and a right backscattered electron image. Background processing for removing the oblique gradient was performed on the upper backscattered electron image, the lower backscattered electron image, the left backscattered electron image, and the right backscattered electron image. In the following description, it is assumed that the upper backscattered electron image, the lower backscattered electron image, the left backscattered electron image, and the right backscattered electron image have undergone background processing.

[0079] The upper backscattered electron image 1200 formed only by the backscattered electrons reaching above the center of the EBSD detector (the three divided regions in the central part at the upper end shown in FIG. 11(a)) is shown in FIG. 12. In the upper backscattered electron image 1200 shown in FIG. 12, uneven contrast due to the unevenness of the sample surface was obtained, and the magnetic domain structure was not clearly visible. This is considered to be due to the reasons described above (the first reason to the second reason).

[0080] The lower backscattered electron image 1300 formed only by the backscattered electrons reaching the lower side (the three divided regions in the center at the lower end shown in Fig. 11(b)) than the center of the EBSD detector is shown in Fig. 13. In the lower backscattered electron image 1300 shown in Fig. 13, a dendritic magnetic domain structure is clearly observed. The brightly observed region corresponds to the magnetic domain with the magnetization direction of -X direction, and the darkly observed region corresponds to the magnetic domain with the magnetization direction of +X direction. However, since the uneven contrast is superimposed in addition to the magnetic domain contrast, it cannot be said that the contrast of the backscattered electron image is formed only by the magnetic domain contrast.

[0081] Therefore, considering the uneven contrast obtained from the upper backscattered electron image 1200 shown in Fig. 12, the result of removing the uneven contrast from the lower backscattered electron image 1300 shown in Fig. 13 as much as possible is the first X-direction magnetic domain contrast enhanced image 1400 shown in Fig. 14. The first X-direction magnetic domain contrast enhanced image 1400 is obtained by adding the pixel value of the upper backscattered electron image 1200 shown in Fig. 12 and the pixel value of the lower backscattered electron image 1300 shown in Fig. 13 in order to relax the uneven contrast. In the first X-direction magnetic domain contrast enhanced image 1400 shown in Fig. 14, compared with the lower backscattered electron image 1300 shown in Fig. 13, the uneven contrast is relaxed and the magnetic domain contrast in the ±X directions becomes clearer. On the other hand, the backscattered electron image created by subtracting the pixel value of the lower backscattered electron image 1300 shown in Fig. 13 from the pixel value of the upper backscattered electron image 1200 shown in Fig. 12 is shown in Fig. 15. In the backscattered electron image shown in Fig. 15, compared with the first X-direction magnetic domain contrast enhanced image 1400 shown in Fig. 14, the uneven contrast is not relaxed and the magnetic domain contrast in the ±X directions is not enhanced.

[0082] Next, the left backscattered electron image 1600 formed only by the backscattered electrons reaching the left side (the three divided regions in the center at the left end shown in Fig. 11(c)) than the center of the EBSD detector is shown in Fig. 16. Also, the right backscattered electron image 1700 formed only by the backscattered electrons reaching the right side (the three divided regions in the center at the right end shown in Fig. 11(d)) than the center of the EBSD detector is shown in Fig. 17.

[0083] In the left-side reflected electron images 1600 and right-side reflected electron images 1700 shown in FIGS. 16 and 17, dendritic magnetic domain structures are clearly observed, but it can be seen that the contrast is different from that of the lower-side reflected electron image 1300 shown in FIG. 13. This is because, as described above, by using the electrons that reach which location of the EBSD detector to construct the reflected electron image, the magnetic domains that appear bright can be changed. The regions where the contrast that appears bright in the left-side reflected electron image 1600 and right-side reflected electron image 1700 shown in FIGS. 16 and 17 is reversed correspond to the regions (= magnetic domains) where the magnetization direction is reversed in the ±Y direction. FIG. 18 shows a Y-direction magnetic domain contrast-enhanced image 1800 created by subtracting the pixel values of the right-side reflected electron image 1700 shown in FIG. 17 from the pixel values of the left-side reflected electron image 1600 shown in FIG. 16. In the Y-direction magnetic domain contrast-enhanced image 1800 shown in FIG. 18, compared with the left-side reflected electron image 1600 shown in FIG. 16 and the right-side reflected electron image 1700 shown in FIG. 17, the uneven contrast is alleviated and the magnetic domain contrast is enhanced. In the Y-direction magnetic domain contrast-enhanced image 1800, the darkest-appearing magnetic domain is the magnetic domain with the magnetization direction in the +Y direction, and the brightest region is the magnetic domain with the magnetization direction in the -Y direction.

[0084] Next, a Y-direction magnetic domain contrast relaxation image 1900 created by adding the pixel values of the left-side reflected electron image 1600 shown in FIG. 16 and the pixel values of the right-side reflected electron image 1700 shown in FIG. 17 is shown in FIG. 19. In the Y-direction magnetic domain contrast relaxation image 1900 shown in FIG. 19, the magnetic domain contrast (magnetic domains with magnetization directions in the +Y direction and -Y direction) that is inverted between the left-side reflected electron image 1600 shown in FIG. 16 and the right-side reflected electron image 1700 shown in FIG. 17 is added together, so that the magnetic domain contrast is relaxed, and magnetic domains with magnetization directions in the +X direction / -X direction can be emphasized. However, in the Y-direction magnetic domain contrast relaxation image 1900, it is difficult to observe the magnetic domain contrast in the ±X direction because the uneven contrast is superimposed on the magnetic domain contrast in the ±X direction. Therefore, when the pixel values of the upper-side reflected electron image 1200 shown in FIG. 12 are subtracted from the pixel values of the Y-direction magnetic domain contrast relaxation image 1900 shown in FIG. 19, a second X-direction magnetic domain contrast enhancement image 2000 shown in FIG. 20 is obtained, the uneven contrast is relaxed, and the magnetic domain contrast in the ±X direction is more emphasized.

[0085] From the above results, a magnetic domain structure map 2100 shown in FIG. 21 is a diagram that visualizes the regions of each magnetic domain and the magnetization directions within each magnetic domain in the observation region of the magnetic domain structure of the sample. The observation region of the crystal orientation of the sample coincides with the observation region of the magnetic domain structure. Therefore, the crystal orientation map 1000 shown in FIG. 10 and the magnetic domain structure map 2100 shown in FIG. 21 are of exactly the same region. Thus, the crystal orientation and the magnetic domain structure can be observed in the same visual field.

[0086] Also, the result of forming a reflected electron image (ordinary reflected electron image) only with the reflected electrons that reached the entire EBSD detector is shown in FIG. 22. In the full-region reflected electron image 2200 shown in FIG. 22, the uneven contrast is superimposed on the magnetic domain contrast, and no knowledge about the magnetization direction within the magnetic domain can be obtained only from this image.

[0087] Note that the embodiments and examples of the present invention described above are merely examples of implementation when implementing the present invention, and the technical scope of the present invention should not be construed in a limited manner by these. That is, the present invention can be implemented in various forms without departing from its technical idea or its main features.

Explanation of Signs

[0088] 110 Scanning electron microscope 111 Optical system 112 Specimen holder 120 EBSD detector 130 Imaging device 140 Information processing device 141 Image acquisition unit 142 Crystal orientation acquisition unit 143 First backscattered electron image creation unit 144 Second backscattered electron image creation unit 145 Magnetic domain structure acquisition unit 310 EBSD image 320 Crystal orientation map 330 Backscattered electron image 510 Arrival position of backscattered electrons when there is no internal magnetic field in the specimen 511 Arrival position of backscattered electrons when there is an internal magnetic field in the +X direction in the specimen 512 Arrival position of backscattered electrons when there is an internal magnetic field in the -X direction in the specimen 611 Arrival position of backscattered electrons when there is an internal magnetic field in the +Y direction in the specimen 612 Arrival position of backscattered electrons when there is an internal magnetic field in the -Y direction in the specimen 701 - 702 Magnetic domains with magnetization directions of ±X adjacent to each other 801 - 802 Magnetic domains with magnetization directions of ±Y adjacent to each other 901 - 902 Magnetic domains with magnetization directions of ±X adjacent to each other 1000 Crystal orientation map 1200 Upper backscattered electron image 1300 Lower backscattered electron image 1400 First X - direction magnetic domain contrast - enhanced image 1600 Left-side reflected electron image 1700 Right-side reflected electron image 1800 Y-direction magnetic domain contrast enhanced image 1900 Y-direction magnetic domain contrast relaxed image 2000 Second X-direction magnetic domain contrast enhanced image 2100 Magnetic domain structure map 2200 Full-area reflected electron image BE Reflected electron DU Migration distance of reflected electrons moving upward in the sample DD Migration distance of reflected electrons moving downward in the sample EP Electron beam probe S Sample

Claims

1. A method for observing magnetic domains in a steel sheet, which uses an electron backscatter diffraction (EBSD) image showing a diffraction pattern of reflected electrons that have reached an EBSD detector by irradiating an electron beam in an electron microscope onto a measurement point of a sample composed of a steel sheet having a body-centered cubic (BCC) structure, comprising: In the EBSD detector, when the electron beam is projected onto the EBSD detector, a direction parallel to the irradiation direction of the projected electron beam is defined as the irradiation parallel direction, a direction antiparallel to the irradiation parallel direction is defined as the irradiation antiparallel direction, and two mutually antiparallel directions perpendicular to the irradiation parallel direction are defined as the first irradiation side direction and the second irradiation side direction, respectively; A sample adjustment step of adjusting the sample so that the sample surface corresponds to the (001) plane of the BCC structure; A sample setting step of setting the sample in the electron microscope such that the [100] direction and the [-100] direction of the crystal correspond to one of the irradiation parallel direction and the irradiation antiparallel direction, and the first irradiation side direction and the second irradiation side direction, and the [010] direction and the [0-10] direction of the crystal correspond to the other; A first reflected electron image creating step of creating a reflected electron image in a partial region of the EBSD image by calculating the intensity of reflected electrons in a partial region of the EBSD image for the sample set in the sample setting step, and performing this by varying the measurement points; A second reflected electron image creating step of creating a reflected electron image in which the contrast derived from magnetic domains having magnetization directions corresponding to the [100] direction and the [-100] direction, or the contrast derived from magnetic domains having magnetization directions corresponding to the [010] direction and the [0-10] direction, is enhanced compared to the reflected electron image, and the contrast derived from the shape of the sample surface is relaxed, based on the reflected electron image created in the first reflected electron image creating step; A magnetic domain structure obtaining step of obtaining information indicating the size, shape, and magnetization direction of each magnetic domain in the sample using the reflected electron image created in the second reflected electron image creating step; and comprising In the first reflected electron image creation step, at least one of a reflected electron image on the anti-irradiation parallel direction side, which is a reflected electron image in at least a part of the region on the anti-irradiation parallel direction side of the EBSD image with respect to the position corresponding to the measurement point, and a reflected electron image on the irradiation parallel direction side, which is a reflected electron image in at least a part of the region on the irradiation parallel direction side of the EBSD image with respect to the position corresponding to the measurement point, and a first irradiation side direction reflected electron image, which is a reflected electron image in at least a part of the region on the first irradiation side direction side of the region of the EBSD image with respect to the position corresponding to the measurement point, and a second irradiation side direction reflected electron image, which is a reflected electron image in at least a part of the region on the second irradiation side direction side of the region of the EBSD image with respect to the position corresponding to the measurement point, are created. A method for observing magnetic domains in a steel plate.

2. In the first reflected electron image creation step, the reflected electron image on the anti-irradiation parallel direction side, the reflected electron image on the irradiation parallel direction side, the first irradiation side direction reflected electron image, and the second irradiation side direction reflected electron image are created. The method for observing magnetic domains in a steel plate according to Claim 1.

3. In the second reflected electron image creation step, by performing addition of the pixel value of the reflected electron image on the anti-irradiation parallel direction side and the pixel value of the reflected electron image on the irradiation parallel direction side, a contrast derived from a magnetic domain having a magnetization direction corresponding to one of the [100] direction and the [-100] direction and the [010] direction and the [0-10] direction is enhanced, and a first irradiation direction magnetic domain contrast enhanced image, which is a reflected electron image in which the contrast derived from the shape of the sample surface is relaxed, is created. By performing subtraction of the pixel value of the first irradiation side direction reflected electron image and the pixel value of the second irradiation side direction reflected electron image, a contrast derived from a magnetic domain having a magnetization direction corresponding to the other is enhanced, and an irradiation side direction magnetic domain contrast enhanced image, which is a reflected electron image in which the contrast derived from the shape of the sample surface is relaxed, is created. The method for observing magnetic domains in a steel plate according to Claim 2.

4. In the first reflected electron image creation step, the reflected electron image on the anti-irradiation parallel direction side, the first irradiation side direction reflected electron image, and the second irradiation side direction reflected electron image are created, and the reflected electron image on the irradiation parallel direction side is not created. The method for observing magnetic domains in a steel plate according to Claim 1.

5. In the second reflected electron image creation step, after performing addition of the pixel values of the first irradiation side direction side reflected electron image and the pixel values of the second irradiation side direction side reflected electron image, subtraction of the pixel values of the irradiation anti-parallel direction side reflected electron image is performed, whereby contrast derived from magnetic domains having a magnetization direction corresponding to one of the [100] direction and the [-100] direction, and the [010] direction and the [0-10] direction is emphasized, and a second irradiation direction magnetic domain contrast enhanced image, which is a reflected electron image in which contrast derived from the shape of the sample surface is relaxed, is created. By performing subtraction of the pixel values of the first irradiation side direction side reflected electron image and the pixel values of the second irradiation side direction side reflected electron image, contrast derived from magnetic domains having a magnetization direction corresponding to the other is emphasized, and an irradiation side direction magnetic domain contrast enhanced image, which is a reflected electron image in which contrast derived from the shape of the sample surface is relaxed, is created. The method for observing magnetic domains in a steel sheet according to claim 2 or 4.

6. In the first reflected electron image creation step, among the divided regions obtained by dividing the region of the EBSD image into a plurality of regions such that at least three regions exist in each of the directions corresponding to the irradiation parallel direction and the irradiation anti-parallel direction, and the directions corresponding to the first irradiation side direction and the second irradiation side direction, without using the pixel values of the divided region closest to the position corresponding to the measurement point in the EBSD image, using the pixel values of the divided region closest to the edge of the EBSD image, reflected electron images in a partial region of the EBSD image are respectively created. The method for observing magnetic domains in a steel sheet according to any one of claims 1 to 5.

7. The reflected electron image created in the first reflected electron image creation step is an image including an observation region of the crystal orientation of the sample analyzed based on the EBSD image. Information indicating the size, shape, and magnetization direction of each magnetic domain in the sample is information of a region including the observation region of the crystal orientation of the sample. The method for observing magnetic domains in a steel sheet according to any one of claims 1 to 6.

Images