A method for measuring the magnetic domain wall movement speed

Abstract

The present invention provides a method for measuring the magnetic domain wall movement speed. By acquiring magnetic domain images at different times, calculating the magnetic domain change images and performing edge recognition, selecting the contour to be analyzed according to the recognized edges, performing circular fitting on the contour to be analyzed, obtaining the corresponding radius and calculating the magnetic domain wall movement speed.

Description

Technical Field

[0001] The present invention belongs to the technical field of magnetic measurement using the magneto - optical effect, and relates to the processing of magneto - optical Kerr images, specifically to a method for measuring the movement speed of magnetic domain walls. Background Art

[0002] The magneto - optical effect includes the Kerr effect and the Faraday magneto - optical effect. Among them, the Kerr effect refers to the phenomenon that when plane - polarized light irradiates the surface of a magnetic material and emits light, the plane of polarization deflects. Since the rotation direction depends on the direction of the magnetization vector in the magnetic domain and the rotation angle is proportional to the magnetization vector, this effect can be used to observe the surface magnetic domain structure of an opaque magnetic body. By observing the deflection of the plane of polarization caused by the magneto - optical effect, the magnetic state of the object to be measured can be obtained, and the corresponding image can be acquired. Figure 1 、 Figure 2 Shows the images obtained by the magneto - optical Kerr effect of the object to be measured at different times. Among them, the magnetism of regions with different brightnesses is different, and the magnetic properties of the object to be measured can be analyzed based on this.

[0003] To analyze the magnetic properties of the object to be measured, studying the movement of magnetic domain walls is an important means. Figure 1 、 Figure 2 Shows the magneto - optical Kerr images of the same region of the object to be measured at different times. It can be seen that Figure 2 the light - colored patch in Figure 1 has a larger range and a different shape compared to the light - colored patch in Figure 1 、 Figure 2 . Analyzing the movement of magnetic domain walls is achieved by analyzing the changes in the patches in

[0004] In the prior art, the commonly used method for measuring the movement speed of magnetic domain walls is manual measurement. The specific process is as follows: First, obtain the images of the initial magnetic domain and the expanded magnetic domain, manually subtract the two images to obtain the region where the magnetic domain expands, as shown in Figure 3 , and on this basis, measure the distance that the magnetic domain wall moves, as shown in Figure 4 . In , by manually drawing a line between the magnetic domain walls and measuring the length of the line segment, the distance that the magnetic domain wall moves is obtained, and then the movement speed of the magnetic domain wall is analyzed. However, when drawing a line between the magnetic domain walls, the measurer needs to subjectively select the drawing direction, and the obtained distance of the magnetic domain wall is greatly affected by subjective factors; at the same time, the edges of the magnetic domain walls are blurred and irregular curves, and how to determine the starting and ending positions of the drawn line is also greatly affected by the subjective selection of the measurer. Therefore, the movement speed of the magnetic domain wall obtained on this basis is also greatly affected by the measurer's subjectivity and cannot be used for subsequent comparative analysis. Summary of the Invention

[0005] In view of the problem in the prior art that the moving speed of magnetic domain walls is subject to the subjective influence of the measurer, the present invention provides a method for measuring the moving speed of magnetic domain walls.

[0006] A method for measuring the moving speed of magnetic domain walls provided by the present invention specifically includes the following steps:

[0007] S1: Obtain the magnetic domain image at time i ;

[0008] S2: Obtain the magnetic domain image at time j ;

[0009] S3: Calculate the magnetic domain change image according to 、 ; ;

[0010] S4: Perform edge recognition on ;

[0011] S5: According to the recognized edges, perform circle fitting on the contours to be analyzed 、 respectively, to obtain the corresponding radii 、 ;

[0012] S6: Calculate the moving speed of the magnetic domain wall .

[0013] Preferably, in S3, by taking the difference between and , is obtained.

[0014] Optionally, in S3, each pixel value in the image is multiplied by a preset value a, and the result is used as the new . Preferably, a ∈ [100, 200].

[0015] Preferably, S4 includes:

[0016] S41: Blur to obtain the image ;

[0017] S42: Convert to a grayscale image to obtain the image ;

[0018] S43: Perform a binarization operation on to obtain the image ;

[0019] S44: Perform edge recognition on .

[0020] Optionally, in S5, at least two of the edges are selected and the surrounding relationship is analyzed, and at least partial regions of two edges having a surrounding relationship are respectively used as the contour 、 。

[0021] Preferably, the minimum circumscribed rectangle of the edge is calculated, and when there is a surrounding relationship between the minimum circumscribed rectangles, the corresponding edges have a surrounding relationship.

[0022] Optionally, when one edge surrounds at least two other edges, the outer edge is used as the secondary edge, the surrounded edges are used as the primary edges, and the secondary edge is decomposed according to the primary edges; one of the primary edges and a partial region of the corresponding secondary edge are used as the first contour , the second contour 。

[0023] Preferably, the secondary edge is decomposed in the following manner:

[0024] Circular fitting is respectively performed on each primary edge, the intersection points of the symmetry center line between each center and the center closest to it and the secondary edge are obtained, and the secondary edge is decomposed into at least two regions; one of the primary edges and the region of the secondary edge closest to the primary edge are respectively used as the contour 、 。

[0025] Preferably, the edge can be an open curve, a closed curve, or a combination of an open curve and a closed curve.

[0026] Preferably, in S4, the first contour and the second contour both have lengths greater than a preset length. Further preferably, the preset length is 100 pixels.

[0027] Preferably, in S5, in combination with the size correspondence between the magnetic domain image 、 and the actual object, calculate 、 。

[0028] Further optionally, after S2 ends, the images with different magnification factors are scaled to the same magnification factor, and then S3 - S6 are performed.

[0029] Preferably, the magnetic domain image 、 has the same size ratio as the actual object.

[0030] The present invention has at least the following beneficial effects: the calculation process excludes the influence of subjective factors, directly compares the radius differences of the fitted circles, and calculates the movement of the magnetic domain walls and the corresponding speeds from the perspective of the overall magnetic domain; through edge recognition, partial irregular twists and blurred edges on the edges are excluded, reducing the amount of calculation and improving the calculation speed. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 The magnetic domain image at the first moment obtained for one embodiment.

[0032] Figure 2 The magnetic domain image at the second moment obtained for one embodiment.

[0033] Figure 3 For use Figure 1 、 Figure 2 The magnetic domain change image calculated from the magnetic domain image.

[0034] Figure 4 Schematic diagram of the existing method for calculating the magnetic domain wall distance.

[0035] Figure 5 The magnetic domain change image after being blurred.

[0036] Figure 6 The magnetic domain change image after being binarized.

[0037] Figure 7 The magnetic domain change image after edge recognition.

[0038] Figure 8 Schematic diagram of the method for identifying the edge enclosure relationship.

[0039] Figure 9 Schematic diagram of the relationship between the contour to be analyzed and the magnetic domain change image for one embodiment.

[0040] Figure 10 Schematic diagram of a method for edge segmentation for one embodiment.

[0041] Figure 11 Schematic diagram of the fitting result of the contour circle. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0042] To make the objectives and features of the present invention more obvious and understandable, the following further describes the specific embodiments of the present invention in conjunction with the accompanying drawings. It should be noted that the accompanying drawings are all in a very simplified form and use non-precise ratios, only for conveniently and clearly assisting in explaining the objectives of the embodiments of the present invention.

[0043] In addition, it should be noted that Figures 3 to 6 、 Figure 9The image shown is the image after the actual image is color-inverted, aiming to facilitate recognition, annotation, and explanation. Those skilled in the art can process the corresponding image data during actual use and perform color inversion on the data according to actual needs.

[0044] A method for measuring the magnetic domain wall movement speed includes the following steps:

[0045] S1: Obtain the magnetic domain image at time i .

[0046] S2: Obtain the magnetic domain image at time j .

[0047] S3: Calculate the magnetic domain change image according to 、 . .

[0048] S4: Perform edge recognition on to obtain the edge recognition result.

[0049] S5: According to the recognized edge, perform circle fitting on the contour to be analyzed respectively 、 to obtain the corresponding radii 、 .

[0050] S6: Calculate the magnetic domain wall movement speed .

[0051] More specifically, in combination with the attached Figures 1 to 11 , the present invention will be described.

[0052] S1: Obtain the magnetic domain image at time i . More specifically, Figure 1 shows the magnetic domain image of a measured object at the first moment , and it can be seen that there are multiple magnetic domains in this image. For example, magnetic domains A, B, C, and D.

[0053] S2: Obtain the magnetic domain image at time j . More specifically, Figure 2 shows the magnetic domain image of a measured object at the second moment , and it can be seen that there are also multiple magnetic domains in this image. For example, magnetic domains A', B', C', and D'. It can be clearly seen that compared with , The positions and ranges of the magnetic domains have changed. For example, magnetic domain A has moved to magnetic domain A', magnetic domain B has moved to magnetic domain B', magnetic domain C has moved to magnetic domain C', and magnetic domain D has moved to magnetic domain D'. Among them, the distances between magnetic domains B and C are relatively close. After movement, magnetic domains B' and C' are connected to form a larger magnetic domain, which is represented by B'(C') here.

[0054] For the convenience of calculation, the magnetic domain image 、 Select the images of the same area of the object to be measured at the same magnification. Of course, it is also possible to select the images of the object to be measured that at least contain a partially overlapping area, and only perform subsequent analysis on the magnetic domains in the overlapping area; or select images with a certain difference in magnification, and after scaling the two images to the same magnification, further perform subsequent analysis.

[0055] S3: According to 、 Calculate the magnetic domain change image , Figure 3 shows a schematic diagram of the magnetic domain change image 、 obtained according to the foregoing Specifically, the magnetic domain change image can be obtained by 、 subtraction. When the contrast of the subtracted image is low, there may

[0056] be a problem that it is difficult to clearly observe and analyze the magnetic domain change. At this time, optionally, the contrast can be increased to enhance the brightness and darkness difference of the image for further analysis. More specifically, the way to increase the contrast can be to multiply each pixel in the image by a preset value a, and the obtained result is used as the new , where a ∈ [100, 200], and the specific value can be adjusted according to the actual effect of the image. For example, Figure 3 the image shown is obtained by multiplying each pixel value by 100 on the basis of the subtraction of 、 . Since 、 the subtracted image already has a certain contrast, so a is selected as 100. When 、 the contrast of the subtracted image is still low, a larger a value needs to be selected, such as 150 or 200. Figure 3 The magnetic domain change image shown Among them, the magnetic domain difference between the i-th moment and the j-th moment is shown, which essentially shows the magnetic domain change range from the i-th moment to the j-th moment, that is, the magnetic domain change image. For example, the area A - A' is essentially the magnetic domain change area from the A magnetic domain to the A' magnetic domain, the area BC - B'(C') is essentially the magnetic domain change area from the B magnetic domain and the C magnetic domain to the B'(C') magnetic domain, and the area D is essentially the magnetic domain change area from the D magnetic domain to the D' magnetic domain.

[0057] S4: Perform edge recognition, and the obtained edge recognition result is as Figure 7 , Figure 9 shown. Figure 7 The edges shown in Figure 1 , Figure 2 are essentially the edges of the magnetic domains in

[0058] . For example, the edge 1 of the area A - A' is essentially the edge of the magnetic domain A, and the edge 2 is essentially the edge of the magnetic domain A'.

[0058] There are various methods to perform edge recognition. In the present invention, preferably, the edge recognition of is performed in the following manner:

[0059] S41: Blur to obtain the image . Figure 5 shows an example of the effect of blurring using a combination of Gaussian blur and mean blur. Specifically, as a preferred solution, Gaussian blur, mean blur, Gaussian blur, mean blur, and Gaussian blur are used in sequence to obtain the effect shown in Figure 5 . It can be seen that the noise in the image is significantly reduced, as well as the influence brought by sample defects.

[0060] S42: Convert to a grayscale image to obtain the image . Since in this embodiment, the magnetic domain image is mainly the magnetic domain image measured by the magneto - optical Kerr effect, the main difference shown in the image is the brightness difference. The effect of converting to a grayscale image is not obvious and is generally basically the same as the image shown in Figure 5 . By converting to a grayscale image, redundant color channel information can be further filtered out, the data volume of the image to be processed can be further reduced, and the image processing speed can be accelerated; at the same time, it can also avoid the influence of other non - obvious colors in the image on the edge recognition result.

[0061] S43: Perform a binarization operation on to obtain the image , as shown in Figure 6 , forFigure 5 Based on this, the result of the binarization operation performed through the binarization threshold can be seen that the image has been converted into a binarized region, and the edges of regions A - A', BC - B'(C'), and D - D' are clear. Among them, the binarization threshold can be determined by the Otsu method.

[0062] S44: For perform edge recognition. As Figure 7 shown, the edges of each region are recognized. For example, the edges 1 and 2 of region A - A', the edges 3, 4, and 5 of region BC - B'(C'), and the edges 6 and 7 of region D - D'.

[0063] It should be noted that since the magnetic domain change image reflects the difference between the initial state and the end state of the magnetic domain, and there are often fuzzy and irregular curves at the edges of the magnetic domain walls, such as radial stripes and zigzag edges. Therefore, by performing a blurring operation, the detailed features of these stripes and zigzag edges can be eliminated, and only the general shape of the magnetic domain is retained. Combining with the binarization operation, the general shape of the magnetic domain can be quickly recognized without paying too much attention to the detailed features, greatly improving the operation efficiency.

[0064] S5: According to the recognized edges, respectively perform circle fitting on the contours to be analyzed , to obtain the corresponding radii , . Taking the edges 1 and 2 of region A - A' shown in Figure 7 as an example. Select the edges 1 and 2 of region A - A' shown in Figure 7 . Taking edge 1 as the contour , perform circle fitting on the contour to obtain the center O1 and radius ; taking edge 2 as the contour , perform circle fitting on the contour to obtain the center O2 and radius . It should be noted that , can be selected according to needs. For example, is the expanded contour, is the contour before expansion. Specifically, edge 1 is included in edge 2, and edge 2 can be used as the expanded contour , and edge 1 is the contour before expansion .

[0065] S6: Calculate the magnetic domain wall movement speed . Still taking Figure 7The edges 1 and 2 shown in [figure] are described. Since the region A-A’ is further calculated from the magnetic domain images at time i and time j, the time between time i and time j is used as the time taken for the magnetic domain wall to move from edge 1 to 2. The time difference between time i and time j in this image is 50 mics. , it can be calculated that

[0066] Through the above process, the calculation of the magnetic domain wall movement speed is realized. Since the movement of the magnetic domain wall is related to the properties of the object under test, the magnetic domain wall usually does not change uniformly along the original magnetic domain, but may have different change amplitudes in different directions. Please refer to Figure 11 , it can be seen that the centers of the fitting circles of the contours before and after the movement of the same group of magnetic domains do not coincide. For example, O1 and O2, O3 and O5-3, O4 and O5-4, O6 and O7, indicating that the centers of the magnetic domain walls before and after the change are not the same. By calculating the magnetic domain wall movement speed using the radius values obtained by circle fitting and calculating the radius differences before and after the change, without paying attention to the center position differences, the magnetic domain wall movement is abstracted into specific parameters, excluding the adverse effects of the non-uniform change of the magnetic domain wall on the calculation of the magnetic domain wall movement speed, and calculating the movement of the magnetic domain wall and the corresponding speed from the perspective of the overall magnetic domain. In addition, through edge recognition, some irregular twists and turns and blurred edges on the edge are excluded, reducing the calculation amount and improving the calculation speed.

[0067] When there are multiple magnetic domains in the magnetic domain image, there will be more than two edges in the edge recognition result obtained through S4. At this time, it is necessary to clarify the corresponding relationship between the edges to select the edges before and after the change of the same magnetic domain as the selected contours 、 for calculation. Therefore, in S5, when selecting the contour to be analyzed according to the recognized edges, corresponding recognition and selection are required. Specifically, the edges can be selected according to the enclosure relationship between the edges. Specifically, in S5, at least two of the edges are selected and the enclosure relationship is analyzed, and at least part of each of the two edges with the enclosure relationship is selected as the contour 、 . Please refer to Figure 8 , which is an example of the enclosure relationship analysis of edges 1 to 7. It can be seen that edge 2 encloses edge 1, edge 5 encloses edges 3 and 4, and edge 7 encloses edge 6. Therefore, edges 1 and 2, edges 3, 4, and 5, edges 6 and 7 are respectively used as the associated edges for subsequent contour selection.

[0068] Figure 8The inclusion relationship analysis shown in the figure is carried out by analyzing the inclusion relationship between the minimum circumscribed rectangles of each edge. For example, the minimum circumscribed rectangle of edge 1 is Am, the minimum circumscribed rectangle of edge 2 is An, and Am is included in An. Accordingly, edge 1 is included in edge 2; the minimum circumscribed rectangle of edge 3 is Bm, the minimum circumscribed rectangle of edge 4 is Cm, the minimum circumscribed rectangle of edge 5 is Bn (Cn), and Bm and Cm are included in Bn (Cn). Accordingly, edge 5 is included in edges 3 and 4; the minimum circumscribed rectangle of edge 6 is Dm, the minimum circumscribed rectangle of edge 7 is Dn, and Dm is included in Dn. Accordingly, edge 6 is included in edge 7. However, Am is not included in Bn (Cn), so edge 1 is not included in edge 5, and there is no relationship between edge 1 and edge 5. It should be noted that for some incomplete edges, such as edges 6 and 7, the inclusion relationship can also be analyzed in the aforementioned manner, that is, when 1-3 sides of the minimum circumscribed rectangle coincide, it is still considered to have an inclusion relationship. For example, there is a collinear edge between the minimum circumscribed rectangles Dn and Dm, and the other edges are not collinear, and it is still determined that Dm is included in Dn.

[0069] Select at least partial regions of two edges with an inclusion relationship respectively as the contour 、 . In particular, for edges with a one-to-one correspondence of inclusion relationships only, select each complete edge as the contour 、 . For edges with an inclusion relationship but a non-one-to-one correspondence of inclusion relationships, divide the outer edge that encloses according to the enclosed edge, and select a part of the divided outer edge and the corresponding enclosed edge respectively as the contour 、 .

[0070] Specifically, as shown by edges 3, 4, and 5 in Figure 8 , there is a situation where one edge encloses multiple edges, which reflects the fusion between magnetic domains. For example, Figure 1 after the expansion of magnetic domains B and C, under specific circumstances, as shown in Figure 2 , the magnetic domains may fuse into B’ (C’). For this situation, it is necessary to divide the region of the outer edge to determine the correspondence between the inner edge and the outer edge in order to calculate the movement speed of the magnetic domain wall.

[0071] For the sake of convenience of explanation, take edge 5 on the outside in Figure 8 as the secondary edge, and edges 3 and 4 on the inside as the primary edges. Specifically, edge 3 is the first primary edge, and edge 4 is the second primary edge. There is no sequence or size relationship between the primary edge and the secondary edge, which is only used to distinguish the edges at different times.

[0072] Perform circular fitting on the first primary edge 3 and the second primary edge 4 respectively to obtain the center positions of the two primary edges. As Figure 10 shown, the center of the first primary edge 3 is O3, and the center of the second primary edge 4 is O4. Calculate the symmetric center line of the two centers. The symmetric center line divides the secondary edge 5 into two regions. As Figure 10 shown, the secondary edge 10 includes a left region and a right region. On this basis, the regions of the primary edge and the secondary edge that are close to each other are used as the contours of the same magnetic domain change image. For example, the region 5-4 on the left side of the secondary edge is closer to the second primary edge 4. Therefore, the second primary edge 4 and the left region 5-4 of the secondary edge are used as the contours of the same magnetic domain change image, and are respectively used as the selected contours 、 ; the region 5-3 on the right side of the secondary edge is closer to the first primary edge 3. Therefore, the first primary edge 3 and the right region 5-3 of the secondary edge are used as the contours of the same magnetic domain change image, and are respectively used as the selected contours 、 。

[0073] Furthermore, the magnetic domain wall movement speed can be calculated. For example, when the first primary edge 3 and the right region 5-3 of the secondary edge are respectively used as the selected contours 、 , taking the right region 5-3 of the secondary edge as the expanded magnetic domain wall and the first primary edge 3 as the magnetic domain wall before expansion, perform circular fitting on the contour 3 and the contour 5-3 respectively to obtain the center O3 and the center O5-3, as well as the radius of the contour 5-3 、the radius of the contour 3 . Further, in combination with , calculate the magnetic domain wall movement speed. The specific calculation method is similar to the calculation of the aforementioned edges 1 and 2, and will not be elaborated here. When the second primary edge 4 and the left region 5-4 of the secondary edge are respectively used as the selected contours 、 , the calculation method is generally the same as the aforementioned method and will not be elaborated here.

[0074] In addition, it should be noted that when one edge surrounds three or more edges, based on the aforementioned method, the secondary edge can be divided into different regions through the symmetric center line of the two closest surrounded primary edges, and the number of divided regions is less than or equal to the number of primary edges.

[0075] The edges participating in the analysis can be open curves or closed curves. The present invention can be effectively applied to open curves, closed curves, or combinations thereof.

[0076] In addition, in S4, asFigure 7 As shown, there are some smaller contours. For the convenience of calculation, to reduce the subsequent calculation amount and improve the calculation speed, and to a certain extent eliminate the influence brought by noises such as defects in the sample, when selecting contours, the contours with too small lengths are screened out to reduce the calculation amount. More specifically, the first contour and the second contour both have lengths greater than a preset length. The preset length is usually 100 pixels.

[0077] When calculating 、 , it is necessary to perform size transformation and calculation on the pixel size measured in the magnetic domain image and the actual size through the corresponding relationship between the magnetic domain image and the actual size.

[0078] The above shows and describes the basic principles, main features and advantages of the present invention. Therefore, the above is only an embodiment of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification is only the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention also includes various equivalent changes and improvements, and these changes and improvements will all fall within the scope of the present invention claimed.

Claims

1. A method for measuring the magnetic domain wall movement speed, characterized in that Including the following steps: S1: Obtain the magnetic domain image P at time i i ; S2: Obtain the magnetic domain image P at time j j ; S3: According to P i , P j Calculate the magnetic domain change image P i-j ; S4: Edge recognition is performed on P i-j ; The edge recognition of P i-j includes: Blurring P i-j to obtain image P'; i-j Converting P' i-j to a grayscale image to obtain image P'' i-j ; Performing binarization on P'' i-j to obtain image P'''; i-j Performing edge recognition on P'''; i-j ​ S5: According to the recognized edges, perform circle fitting on the first contour m and the second contour n to be analyzed respectively, and obtain the corresponding radii r m , r n ; Select at least two of the edges and analyze the enclosure relationship. Select at least partial regions of the two edges with the enclosure relationship as the first contour m and the second contour n respectively; When one edge encloses at least two other edges, the outer edge is used as the secondary edge, and the enclosed edge is used as the primary edge. Decompose the secondary edge according to the primary edge; Use one of the primary edges and a partial region of the corresponding secondary edge as the first contour m and the second contour n; The secondary edge is decomposed in the following way: Perform circle fitting on each primary edge respectively, obtain the intersection points of the symmetry centerlines between each center and its closest center with the secondary edge, and decompose the secondary edge into at least two regions; Use one of the primary edges and the region of the secondary edge closest to the primary edge as the first contour m and the second contour n respectively; S6: Calculate the magnetic domain wall movement speed V = (r m - r n ) / t i-j .

2. The method for measuring the magnetic domain wall movement speed according to claim 1, wherein: In S3, by subtracting P i from P j , P i-j is obtained.

3. The method for measuring the magnetic domain wall movement speed according to claim 1, characterized in that: In S3, multiply each pixel value in the image P i-j by a preset value a, and use the result as the new P i-j .

4. The measuring method of magnetic domain wall movement speed according to claim 3, characterized in that: a∈[100,200]。 5. The method for measuring the magnetic domain wall movement speed according to claim 1, wherein: Calculating the minimum circumscribed rectangle of the edge, when there is an enclosing relationship between the minimum circumscribed rectangles, there is an enclosing relationship between the corresponding edges.

6. The method for measuring the magnetic domain wall movement speed according to claim 1, wherein: The edge is an open curve; or, The edge is a closed curve; or, The edge is a combination of an open curve and a closed curve.

7. The method for measuring the magnetic domain wall movement speed according to claim 1, characterized in that: In S4, the lengths of the first contour m and the second contour n are both greater than a preset length.

8. A method for measuring the magnetic domain wall movement speed according to claim 1, characterized in that: In S5, in combination with the magnetic domain images P i , P j and the size correspondence relationship with the actual object, calculate r m , r n .

9. The method for measuring the magnetic domain wall movement speed according to claim 1, characterized in that: The magnetic domain image P i , P j has the same size ratio as the actual object.

10. An image processing apparatus, characterized in that: Including a memory and a processor; the processor is used to be coupled with the memory, read and execute instructions in the memory, so that the terminal device implements the method according to any one of claims 1-9.

11. A readable storage medium, characterized in that: A computer program is stored on the readable storage medium; when the computer program is executed, the method according to any one of claims 1-9 is implemented.

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