Electromagnetic coil generated magnetic field calibration method based on magnetic domain wall motion speed ratio

Abstract

The application provides a magnetic field strength calibration method of an electromagnetic coil based on a magnetic domain wall motion speed ratio, which comprises the following steps: measuring the magnetic domain wall motion speed and the corresponding magnetic field strength of a standard sample in a magnetic field generated by a known electromagnetic coil, measuring the magnetic domain wall motion speed and the expected magnetic field strength of the standard sample under the action of a magnetic field generated by a to-be-calibrated electromagnetic coil, calculating a calibration coefficient according to the magnetic domain wall motion speed and the magnetic field strength, and correcting the current-magnetic field mapping relationship of the to-be-calibrated electromagnetic coil according to the calibration coefficient.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of measuring magnetic variables, and relates to the calibration of an electromagnetic coil, in particular to a method for calibrating the magnetic field strength of an electromagnetic coil based on the speed ratio of magnetic domain wall movement. BACKGROUND

[0002] A magnetic field generating device is a device for providing a magnetic field environment, and is one of the key devices in production and research related to the magnetism of an object. In order to meet the corresponding production, processing and testing needs, the magnetic field generating device needs to be able to generate a corresponding magnetic field as needed.

[0003] The most commonly used device for generating a magnetic field is an electromagnet, which has a magnetic core for adjusting at least the shape, strength and range of the magnetic field. Since the magnetic core needs to undergo a magnetization process in the electromagnet, and the magnetic core further increases the time of the magnetization process due to the presence of residual magnetism when it undergoes magnetization, it reduces the change speed of the available magnetic field generated by the electromagnet. Even if a power ferrite material suitable for high frequency conditions is used as the material of the magnetic core, due to the limitations of its own principle, it is still inevitable to make the change speed of the magnetic field generated by the electromagnet relatively low, more specifically, significantly lower than the change speed of the input current. Therefore, in order to obtain a rapidly changing magnetic field, a magnetic coreless electromagnetic coil can be used.

[0004] By using a magnetic coreless electromagnetic coil, a fast magnetic field with a rising edge of nanoseconds can be generated. Before actually using the electromagnetic coil as a magnetic field generator, the electromagnetic coil needs to be calibrated to determine its actual performance, and the magnetic field generated by the electromagnetic coil needs to be measured. The existing magnetic field measurement using Hall effect devices is difficult to effectively measure pulse magnetic fields with a large magnetic field change rate, because there is electromagnetic interference between the current and the signal line of the measurement device. Although there are research results based on Hall effect devices of InAs film to measure strong pulse magnetic fields, they can measure pulse magnetic fields with a magnetic field change rate of 10 5 T / S (Soika, A.K., Sologub, I.O. Measurements of strong pulsed magnetic fields by Hall effect devices. Instrum Exp Tech 53, 122-123 (2010).), but it is still far from measuring magnetic field pulses with a magnetic field change rate of nanoseconds (about 10 7 T / S -10 9 T / S), and thus cannot calibrate electromagnetic coils with nanosecond fast magnetic fields. SUMMARY

[0005] In order to solve the technical problem that the prior art cannot calibrate the electromagnetic coil of the rapid magnetic field, the application provides a magnetic field strength calibration method of an electromagnetic coil based on a magnetic domain wall movement speed ratio, the magnetic domain wall movement speed of a standard sample in a magnetic field generated by a known electromagnetic coil is measured, and the magnetic field strength of a measurement area is obtained; the magnetic domain wall movement speed of the standard sample under the action of a magnetic field generated by a to-be-calibrated electromagnetic coil is measured, the magnetic field strength of the measurement area is calculated according to a preset current magnetic field mapping relationship of the to-be-calibrated electromagnetic coil; and the calibration coefficient is calculated according to the magnetic domain wall movement speed and the magnetic field strength, and the preset current magnetic field mapping relationship is corrected according to the calibration coefficient.

[0006] The known electromagnetic coil in the application mainly refers to that the relationship between the current and the magnetic field of a preset position is known, the preset position generally refers to at least part of a measurement area measured by using the electromagnetic coil as a magnetic field generating device, and more specifically, the mapping relationship between the current size of the known electromagnetic coil and the magnetic field strength in the measurement area is known, and the magnetic field strength in the measurement area can be calculated at least by the current size. The to-be-calibrated electromagnetic coil in the application does not mean that the electromagnetic coil has not been formed or is completely unknown, but means that the actual relationship between the current and the magnetic field of a preset position of the electromagnetic coil is unknown, although the actual current magnetic field relationship is unknown, but according to the actual structure of the electromagnetic coil, the theoretical relationship between the current and the magnetic field can be known on the basis of the prior art. The calibration of the to-be-calibrated electromagnetic coil mainly refers to the correction of the theoretical relationship between the current and the magnetic field, so as to form the actual current and magnetic field relationship. The relationship between the current and the magnetic field more specifically refers to the size relationship between the current size of the electromagnetic coil and the magnetic field strength in the measurement area.

[0007] Preferably, the magnetic domain image is obtained by one of the following methods: magneto-optical Kerr effect, magnetic force microscopy, Lorentz microscopy, magnetic circular dichroism, and electron microscopy, and the magnetic domain wall movement speed is calculated according to the magnetic domain image.

[0008] Preferably, when the known electromagnetic coil and the to-be-calibrated electromagnetic coil drive the magnetic domain wall movement of the standard sample, the standard sample has the same temperature.

[0009] Preferably, the magnetic domain wall movement speed is calculated by the following method:

[0010] The magnetic domain image at the first time is obtained;

[0011] A magnetic field excitation with a time width of T is applied to the sample, and after the excitation is completed, the magnetic domain image at the second time is obtained;

[0012] According to the magnetic domain images at the first time and the second time, the magnetic domain wall movement distance is obtained by comparing the corresponding magnetic domain wall positions.

[0013] According to the magnetic domain movement distance and the time width T, the magnetic domain wall movement speed is calculated.

[0014] Optionally, the magnetic domain images at the first time and the second time are subtracted to obtain a magnetic domain movement area image; and the magnetic domain wall movement distance is obtained according to the magnetic domain area movement image.

[0015] Optionally, the sample is provided with magnetic domains in the measurement range before the magnetic domain wall movement speed is calculated.

[0016] Optionally, the temperature of the sample when the electromagnetic coil is used is the same as the temperature of the sample when the known electromagnetic coil is used when the magnetic domain wall movement speed is measured.

[0017] Optionally, the sample is provided with consistent magnetic domains in the measurement range before the magnetic domain wall movement speed is calculated, and a current is passed through the electromagnetic coil to generate a magnetic field pulse to form an initial magnetic domain wall on the sample.

[0018] Preferably, the initial magnetic domain wall is circular.

[0019] Preferably, the magnetic domain image is obtained by magneto-optical Kerr effect, and the axis of the electromagnetic coil is located in the light spot area for generating the magneto-optical Kerr effect.

[0020] Preferably, the range of the measurement area for calculating the magnetic domain wall movement speed is smaller than the range of the light spot area for generating the magneto-optical Kerr effect.

[0021] Preferably, the magnetic domain wall movement speed v1 in the magnetic field generated by the known electromagnetic coil is measured, the corresponding magnetic field strength H1 is recorded, a plurality of sets of v1 and H1 are obtained, and a linear relationship between H1 and Inv1 is fitted to obtain the intercept b1 and the slope k1 of the linear relationship. -1 / 4

[0022] The magnetic domain wall movement speed v2 in the magnetic field generated by the electromagnetic coil to be calibrated is measured, the magnetic field strength of the measurement area is calculated according to the preset current-magnetic field mapping relationship, the corresponding magnetic field strength H2 is recorded, a plurality of sets of v2 and H2 are obtained, and a linear relationship between H2 and Inv2 is fitted to obtain the intercept b2 and the slope k2 of the linear relationship. -1 / 4

[0023] The calibration coefficient is a2=(k1 / k2) 4 .

[0024] Further preferably, the magnetic field B2 generated by the electromagnetic coil to be calibrated is B2=a0a2I, where I is the current passing through the electromagnetic coil to be calibrated, and a0 is the preset current-magnetic field mapping parameter of the electromagnetic coil to be calibrated. ​​

[0025] Optionally, if b2≠b1, re-adjust the position of the electromagnetic coil to be calibrated, re-acquire v2, H2, and use the re-acquired v2, H2 to fit H2 -1 / 4 linear relationship between Inv2 and Inv1 and acquire b2, k2 until b2=b1.

[0026] Preferably, the magnetic domain image is acquired by magneto-optical Kerr effect, which at least includes polar magneto-optical Kerr effect, and the electromagnetic coil generates a vertical magnetic field at least in the measurement area of the standard sample, which has a magnetic field component perpendicular to the measured surface of the standard sample.

[0027] The application also provides an electromagnetic coil generated magnetic field strength calibration device based on magnetic domain wall motion speed comparison, comprising a magnetic domain image acquisition device, a current acquisition device, a known electromagnetic coil, an electromagnetic coil to be calibrated, a standard sample, a power supply, a timer, and an analysis device, wherein the magnetic domain image acquisition device acquires the magnetic domain image of the standard sample, the timer is used to acquire the energization time of the electromagnetic coil, and the analysis device is in communication connection with the magnetic domain image acquisition device, the current acquisition device, and the timer.

[0028] In the first state, the known electromagnetic coil is close to the standard sample and located at a preset position, the power supply is in electrical connection with the known electromagnetic coil, and the current acquisition device is used to measure the current value flowing into the known electromagnetic coil.

[0029] In the second state, the electromagnetic coil to be calibrated is close to the standard sample and located at the preset position, the power supply is in electrical connection with the electromagnetic coil to be calibrated, and the current acquisition device is used to measure the current value flowing into the known electromagnetic coil. Preferably, the magnetic domain image acquisition device is at least one of a magneto-optical Kerr device, a Lorentz microscope device, and an electron microscope device. Further preferably, the magnetic domain image acquisition device is a magneto-optical Kerr device.

[0030] The application also provides another electromagnetic coil generated magnetic field strength calibration device based on magnetic domain wall motion speed comparison, comprising a magnetic domain image acquisition device, a known electromagnetic coil, an electromagnetic coil to be calibrated, a standard sample, a power supply, and an analysis device, wherein the magnetic domain image acquisition device acquires the magnetic domain image of the standard sample, the power supply is used to provide a preset time width and intensity of current to the known electromagnetic coil and the electromagnetic coil to be calibrated, and the analysis device is in communication connection with the magnetic domain image acquisition device, the current acquisition device, and the power supply.

[0031] In the first state, the known electromagnetic coil is close to the standard sample and located at a preset position, the power supply is in electrical connection with the known electromagnetic coil.

[0032] In the second state, the electromagnetic coil to be calibrated is close to the standard sample and located at the preset position, and the power supply is electrically connected with the electromagnetic coil to be calibrated.

[0033] The application further provides an electromagnetic coil calibration device, characterized by comprising a memory and a processor; the processor is used for coupling with the memory, reading and executing instructions in the memory, so that the calibration device realizes the electromagnetic coil calibration method.

[0034] The application further comprises a readable storage medium, characterized by that the readable storage medium stores a computer program; the computer program realizes the electromagnetic coil calibration method when executed.

[0035] The application has at least the following beneficial effects: the calibration of the electromagnetic coil to be calibrated is completed by using the known electromagnetic coil, the electromagnetic coil generating nanosecond-level fast magnetic field can be calibrated, and the calibration can be completed without using additional equipment even when the space is limited. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 The figure is a linear relationship fitting result of an embodiment of the application. DETAILED DESCRIPTION

[0037] In order to make the purpose and features of the application more obvious and easy to understand, the specific embodiments of the application are further described below in combination with the drawings. It should be noted that the drawings are very simplified and use non-precise ratios, and are only used for the purpose of conveniently and clearly assisting the description of the embodiments of the application.

[0038] The application provides a magnetic field strength calibration method based on magnetic domain wall motion speed ratio of an electromagnetic coil, which calibrates the generated magnetic field of the electromagnetic coil to be calibrated by using a known electromagnetic coil and a standard sample, that is, calibrates the magnetic field generated by the electromagnetic coil. More specifically, the magnetic domain wall motion speed of the standard sample in the magnetic field generated by the known electromagnetic coil is measured to obtain the magnetic field strength at the corresponding position; the magnetic domain wall motion speed of the standard sample under the action of the magnetic field generated by the electromagnetic coil to be calibrated is measured, and the magnetic field strength of the measurement region is calculated according to the preset current-magnetic field mapping relationship of the electromagnetic coil to be calibrated; the calibration coefficient is calculated according to the magnetic domain wall motion speed and the magnetic field strength, and the preset current-magnetic field mapping relationship is corrected according to the calibration coefficient. The application calibrates the generated magnetic field strength of the electromagnetic coil to be calibrated by using the known electromagnetic coil, uses the characteristics that the free layer of the standard sample flips at the nanosecond level and the position of the magnetic domain wall changes, can calibrate the electromagnetic coil generating the nanosecond-level fast magnetic field, solves the problem that the existing technology is difficult to calibrate the magnetic field generating device generating the nanosecond-level fast magnetic field, does not need to use additional equipment, only needs to disassemble and assemble the known electromagnetic coil and the electromagnetic coil to be calibrated, can disassemble and assemble the corresponding electromagnetic coil on the equipment needing to set the electromagnetic coil, does not need to occupy new space except the space where the original electromagnetic coil is located and the original disassembly and assembly space, and can still complete the calibration when the space limitation is large. In addition, the electromagnetic coil generating the fast magnetic field generally has a small volume, and it is difficult for the magnetic sensor to extend into or be set at the calibration position, which leads to the fact that the calibration cannot be performed. The application does not need to use the magnetic sensor and can still effectively calibrate the electromagnetic coil when the space limitation is large.

[0039] For the known electromagnetic coil, since the performance of the electromagnetic coil is known, that is, the mapping relationship of B1=a1I when the electromagnetic coil is actually used is known, wherein B1 is the magnetic field strength at a preset position, and a1 is the magnetic field-current mapping parameter of the electromagnetic coil, therefore, when the electromagnetic coil drives the magnetic domain motion on the standard sample, the magnetic field strength at the corresponding position can be controlled by controlling the size of the current flowing into the electromagnetic coil. Since the performance of the electromagnetic coil is known, the current-magnetic field relationship of the electromagnetic coil is known, the size of the current flowing into the electromagnetic coil can be measured by a current measuring device, or the magnetic field strength can be directly calculated by a power supply capable of setting the output current. More specifically, the known current-magnetic field relationship can refer to the current flowing into the electromagnetic coil and the magnetic field at the position driving the magnetic domain wall motion on the standard sample.

[0040] The electromagnetic coil to be calibrated is mainly the relationship between the current size of the electromagnetic coil and the actual magnetic field strength. It should be noted that the relationship between the current size of the electromagnetic coil and the magnetic field strength in theory is known, that is, the preset current-magnetic field mapping relationship of the electromagnetic coil to be calibrated is known. However, due to the influence of non-ideal factors in the actual structure, the relationship between the current size of the actual electromagnetic coil and the magnetic field strength is unknown, that is, the current-magnetic field mapping relationship is unknown. However, the unknown current-magnetic field mapping relationship has certain correlation with the theoretical current-magnetic field mapping relationship, and the actual current-magnetic field mapping relationship can be obtained by correcting the theoretical current-magnetic field mapping relationship.

[0041] The position of driving the domain wall motion on the standard sample is usually a region, that is, a measurement region. However, the range of the region is usually small, and the difference in magnetic field strength in the range is small, so the magnetic field strength of the region can be represented by the magnetic field strength of a point in the region. For example, when the region is circular, the point is the center of the circle, and the magnetic field strength at the center of the circle is regarded as the magnetic field strength of the measurement region.

[0042] Since the main purpose of measuring the domain wall motion speed is to compare the difference in domain wall motion speed under the action of different electromagnetic coils, a standard sample capable of generating a relatively obvious magnetic domain and a magnetic domain wall capable of moving under the action of an external magnetic field is required. In this embodiment, a magnetic thin film can be selected as the standard sample. In addition, other types of magnetic materials can also be selected as needed. In order to facilitate the magnetic field of the electromagnetic coil to induce the magnetic domain wall motion on the standard sample, the standard sample can adopt a thin standard sample to measure the magnetic domain wall motion in a larger measurement region and reduce the performance requirements of the magnetic field required to induce the magnetic domain wall motion.

[0043] In the observation method of the magnetic domain wall motion, the magneto-optical effect can directly obtain the state of the magnetic domain wall and analyze the magnetic domain wall motion speed. Specifically, the magnetic domain images at different times can be obtained through the magneto-optical Kerr effect, and the magnetic domain wall motion speed is calculated according to the obtained magnetic domain images. In addition, since the electromagnetic coil is mainly calibrated by the magnetic domain wall motion speed, other magnetic imaging methods capable of obtaining the magnetic domain wall can be used in the present application, such as magneto-optical Kerr effect, magnetic force microscope, Lorentz microscopy, magnetic circular dichroism, electron microscopy, etc. More specifically, the aforementioned electron microscopy can include spin-polarized low-energy electron microscopy, spin-polarized scanning tunneling microscopy, and other magnetic domain imaging methods.

[0044] It should be noted that when the magnetic domain wall movement of the known electromagnetic coil and the sample to be calibrated is driven, the sample needs to have the same temperature. Here, the temperature mainly refers to the temperature of the sample itself, rather than the temperature of the environment in which the sample is located. When the sample has a temperature change during the magnetic domain wall movement, the temperature change also needs to be as same as possible. Here, the same does not mean that the temperature is completely consistent, but that the temperature is generally similar or the same, and the difference in temperature has little effect on the magnetic domain wall movement so as to be ignored.

[0045] When the magnetic domain image is obtained by using the magneto-optical Kerr effect and the magnetic domain wall movement speed is calculated, the following method can be used for calculation:

[0046] Obtain the magnetic domain image at the first time;

[0047] Apply a magnetic field excitation with a time width of T to the sample, and after the excitation is completed, obtain the magnetic domain image at the second time;

[0048] According to the magnetic domain images at the first time and the second time, compare the corresponding magnetic domain wall positions to obtain the magnetic domain wall movement distance;

[0049] According to the magnetic domain movement distance and the time width T, calculate the magnetic domain wall movement speed.

[0050] Wherein, the movement distance of the magnetic domain wall can be obtained by manually measuring the magnetic domain position in the magnetic domain image at the first time and the magnetic domain position in the magnetic domain image at the second time, analyzing the position difference between the two magnetic domain positions in the image, further calculating the actual position difference in combination with the transformation relationship between the image and the actual size, and combining the time used for the magnetic domain wall change to calculate the magnetic domain wall movement speed. In some cases, the time of the magnetic field excitation can be used as the time used for the magnetic domain wall change, and more specifically, the time width T of the magnetic field excitation can be used as the time used for the magnetic domain wall change.

[0051] When analyzing the magnetic domain position difference, the two magnetic domain images can also be subtracted to form an image of the magnetic domain change region. The start and end positions of the magnetic domain wall movement are essentially the inner and outer edges of the magnetic domain change region. The actual movement distance of the magnetic domain wall can be obtained by measuring and transforming the distance between the edges, and then the magnetic domain wall movement speed can be obtained.

[0052] In acquiring the time between the first time and the second time, the parameter of the current flowing into the electromagnetic coil can be acquired by control, or the current time is determined, for example, a single pulse current is flowed into, and the pulse width of the current is controlled as T, then the time of the magnetic field generated by the electromagnetic coil is substantially the same as the pulse width of the current, that is, the time width of the magnetic field generated by the electromagnetic coil is T; when the time of the current flowing into the electromagnetic coil is controlled, then the time of the magnetic field generated by the electromagnetic coil is substantially the same as the time of the current flowing into the electromagnetic coil, for example, the time width of the current output by the power supply electromagnetic coil is controlled as T, then the time width of the magnetic field generated by the electromagnetic coil is T.

[0053] The aforementioned sample for measuring the domain wall movement speed needs to have the movement of the domain wall in the observation range and calculate the domain wall movement speed. In view of the accuracy, intuitiveness and convenience of the calculation of the domain wall movement speed, before the calculation of the domain wall movement speed, the sample has the domain wall in the measurement range, so that the domain wall movement speed can be calculated after the first driving of the domain wall movement. In addition, before the calculation of the domain wall movement speed, the sample has the consistent domain at least in the measurement range, so that the measurement range is the same domain and has no domain wall, and the current is passed to the electromagnetic coil to generate a single pulse magnetic field, so as to form an initial domain wall in the measurement range on the sample. On the one hand, it is convenient for subsequent calculation of the domain wall movement speed, and on the other hand, it can exclude the influence of the domain wall of other domains on the edge measurement of the driven domain wall, reduce the calculation difficulty caused by the fusion between the domains, and facilitate the observation of the domain wall and the measurement of the domain wall movement. For the measurement range being the same domain and having no domain wall, the sample can be in a saturated magnetization state. When the initial domain wall is formed in the measurement range on the sample by the single pulse magnetic field, the initial domain wall is preferably circular. If the initial domain wall is not circular, it indicates that the magnetic field is not uniform near the initial domain wall, that is, the magnetic field strength in different directions of the initial domain wall is different and causes the position difference of the initial domain in different directions. At this time, the position of the electromagnetic coil needs to be adjusted to adjust the magnetic field strength near the initial domain. The shape of the initial domain wall generated by the driving electromagnetic coil on the sample can be observed to determine whether the electromagnetic coil is located in the measurement area. For example, when the initial domain wall is close to circular, it indicates that the electromagnetic coil is located in the measurement area; when the initial domain wall is not circular, for example, in the form of an oblong, it indicates that the axis of the electromagnetic coil deviates from the measurement area. The position of the electromagnetic coil can be further adjusted as needed, for example, according to the direction of the long axis and the short axis of the ellipse, to adjust the position of the electromagnetic coil. It should be noted that the circular shape of the initial domain wall here refers to the initial domain wall being generally circular or close to circular, rather than an ideal circle. Since the domain wall image often has blur, or the domain wall itself is composed of irregularly shaped domain walls in detail, it may have some tortuous or blurred areas, so that the domain wall is difficult to achieve an ideal circle, but it is possible to have a generally circular overall shape, for example, a circular domain wall composed of a large number of fine broken lines, curves or straight lines and the like, or a circular arc-shaped domain wall composed of fine broken lines, curves or straight lines, and similar domain walls with generally circular or arc-shaped shapes. In addition, the aforementioned initial domain wall being circular is only one optional scheme, and it can be understood that the initial domain wall can also not be circular as long as the calculation of the domain wall movement speed can be realized.

[0054] In order to fit the current magnetic field mapping relationship, a plurality of sets of data need to be obtained, that is, the magnetic domain wall needs to be moved multiple times by using the electromagnetic coil, and the magnetic domain wall movement speed needs to be calculated. In this process, the positions of the magnetic domain wall before and after the movement need to be determined, that is, the initial state of the magnetic domain wall before the movement and the state to which the magnetic domain wall moves are not the primary consideration; the positions of the magnetic domain wall before and after the movement need to be determined and correspond to each other so as to calculate the magnetic domain wall movement distance.

[0055] In order to further enable the movement of the magnetic domain wall to be observed, when the magnetic domain image is obtained by the magneto-optical Kerr effect, the axis of the electromagnetic coil is located in the light spot area in which the magneto-optical Kerr effect is generated, that is, the magnetic field generated by the electromagnetic coil at least partially exists in the uniform magnetic field in the observation range of the magneto-optical Kerr device. Alternatively, the size of the light spot irradiated on the sample is greater than the movement range of the observed magnetic domain wall; the range of the measurement area used to calculate the magnetic domain wall movement speed is smaller than the range of the light spot area used to generate the magneto-optical Kerr effect.

[0056] When the magneto-optical Kerr effect is used as the magnetic domain image acquisition method, in order to make the magneto-optical Kerr effect more obvious, as a preferred scheme, the magneto-optical Kerr effect at least includes the polar magneto-optical Kerr effect, and the electromagnetic coil generates at least a vertical magnetic field existing in the magnetic field component perpendicular to the measured surface of the sample in the measurement area of the sample. Specifically, the magnetic field in the measurement area is not a completely directed magnetic field, but a magnetic field whose difference is controlled within an acceptable range, and the magnetic field at the selected position is used as a general representation of the magnetic field in the measurement area. Since the measurement area itself is a range, in combination with the distribution characteristics of the magnetic field generated by the electromagnetic coil, it can be known that the magnetic field generated by the electromagnetic coil in the measurement area is not completely parallel, and in the embodiment, the magnetic field component perpendicular to the measured surface of the sample is mainly utilized, but actually the magnetic field generated by the electromagnetic coil still exists in the measurement area. The magnetic field component not perpendicular to the measured surface of the sample, for the magnetic field component not perpendicular to the measured surface of the sample, the actual test requirements can be limited to make the magnetic field generated by the electromagnetic coil in the measured area mainly the magnetic field component perpendicular to the measured surface of the sample, and the magnetic field component not perpendicular to the measured surface of the sample can be ignored, so as to facilitate control and calculation.

[0057] In the present application, the accuracy of the calculation of the magnetic domain wall movement speed is improved, and the reliability of the correction coefficient can be effectively improved. Therefore, the accuracy improvement method described above needs to be selected according to actual needs to improve the correction effect.

[0058] Next, a more specific correction process is given.

[0059] The magnetic domain wall movement speed v1 in the magnetic field generated by the known electromagnetic coil is measured multiple times, the corresponding magnetic field intensity H1 is recorded, and H1 -1 / 4The linear relationship between Inv1 and Inv2 is fitted, and the slope k1 of the linear relationship is obtained. In this process, since the electromagnetic coil is known, i.e. the magnetic field-current mapping relationship or matching relationship in the measurement range of the standard sample is known, therefore, based on this, the magnetic field strength value in the measurement range can be determined according to the current value input into the known electromagnetic coil. More specifically, when the magnetic field-current mapping relationship is known, the magnetic field strength can be calculated through the mapping relationship; when the magnetic field-current matching relationship is known, the current input into the electromagnetic coil can be set to be equal to a certain current in the matching relationship, so as to know the corresponding magnetic field strength. Figure 1 A linear relationship obtained by fitting in an embodiment is shown, wherein, f1 H1 is the magnetic field strength of the known electromagnetic coil -1 / 4 The linear relationship between Inv1 and Inv2 is fitted.

[0060] The magnetic domain wall motion speed v2 in the magnetic field generated by the to-be-calibrated electromagnetic coil is measured multiple times, the magnetic field strength of the measurement region is calculated according to the preset current-magnetic field mapping relationship, the corresponding magnetic field strength H2 is recorded, the H2 -1 / 4 The linear relationship between Inv2 and Inv1 is fitted, and the intercept b2 of the fitted linear relationship is set to be b1, as shown in Figure 1 f2 The slope k2 of the linear relationship is obtained. In this process, the recorded magnetic field strength H2 is not the real magnetic field strength of the measurement region, but a theoretical prediction value. Specifically, although there is a preset current-magnetic field mapping relationship, since the to-be-calibrated electromagnetic coil has not been calibrated and corrected, the actual magnetic field strength generated by the electromagnetic coil in the measurement region cannot be known, therefore, the current-magnetic field mapping relationship needs to be corrected to correct the difference between the theoretical relationship and the actual relationship, therefore, the theoretical value H2 needs to be recorded, and the deviation between the preset mapping relationship and the actual mapping relationship is inferred based on this.

[0061] If b2≠b1, it indicates that there is a difference in the measurement conditions between the to-be-calibrated electromagnetic coil and the known electromagnetic coil, and the measurement result cannot be used to calculate the calibration coefficient. When b2≠b1, at least the position of the to-be-calibrated electromagnetic coil needs to be adjusted again, for example, so that the relative position of the to-be-calibrated electromagnetic coil and the known electromagnetic coil with the standard sample is the same, v2 and H2 are reacquired, and H2 -1 / 4 ​The linear relationship between the Inv2 and the b2, k2 are obtained until the b2=b1. In addition, the temperature of the sample when the magnetic domain wall movement speed is measured should be the same as the temperature of the sample when the known electromagnetic coil is used. In addition, the temperature of the electromagnetic coil to be calibrated should be controlled and the temperature of the electromagnetic coil to be calibrated should be substantially the same as the temperature of the known electromagnetic coil. The degree of adjustment of the position and the degree of maintaining the temperature can be selected and adjusted according to the accuracy requirement.

[0062] The magnetic domain wall movement speed of the sample in the magnetic field generated by the known electromagnetic coil and the magnetic domain wall movement speed of the sample in the magnetic field generated by the electromagnetic coil to be calibrated have no sequence and only need to be completed before the calibration coefficient is calculated.

[0063] After the k1 and the k2 are obtained, the calibration coefficient a2=(k1 / k2) is calculated. 4 The preset current magnetic field relationship of the electromagnetic coil to be calibrated is corrected by using the calibration coefficient so that the preset current magnetic field relationship is close to the actual current magnetic field relationship.

[0064] Further, the preset current magnetic field relationship of the electromagnetic coil to be calibrated after the correction is B2=a0a2I, wherein the I is the current through the electromagnetic coil to be calibrated, and the a0 is a preset current magnetic field mapping parameter which is used when the theoretical magnetic field strength is calculated.

[0065] The application also provides an electromagnetic coil generated magnetic field strength calibration device based on the magnetic domain wall movement speed comparison, which comprises a magnetic domain image acquisition device, a current acquisition device, a known electromagnetic coil, an electromagnetic coil to be calibrated, a sample, a power supply, a timer, an analysis device, the magnetic domain image acquisition device acquires the magnetic domain image of the sample, the timer is used to acquire the energization time of the electromagnetic coil, and the analysis device is in communication connection with the magnetic domain image acquisition device, the current acquisition device and the timer.

[0066] In the first state, the known electromagnetic coil is close to the sample and located at a preset position, the power supply is electrically connected with the known electromagnetic coil, and the current acquisition device is used to measure the current value of the known electromagnetic coil.

[0067] In the second state, the electromagnetic coil to be calibrated is close to the sample and located at a preset position, the power supply is electrically connected with the electromagnetic coil to be calibrated, and the current acquisition device is used to measure the current value of the known electromagnetic coil.

[0068] For the aforementioned preset position, it refers to the relative position between the electromagnetic coil and the measurement area determined before measurement. For example, in order to make the magnetic domain wall on the sample move obviously, the measurement area of the sample is determined in advance, and the position, distance, angle and other parameters of the electromagnetic coil and the measurement area are determined in advance. It should be noted that the electromagnetic coil to be measured and the known electromagnetic coil need to be arranged at the same position, that is, the relative position between the electromagnetic coil and the measured area when measuring the magnetic domain wall movement driven by the known electromagnetic coil is the same as the relative position between the electromagnetic coil and the measured area when measuring the magnetic domain wall movement driven by the electromagnetic coil at the measurement position.

[0069] It should be noted that the timer refers to a device for collecting the energization time of the electromagnetic coil, which may not have a timing function or be an independent device. For example, when the energization time parameter is directly set in the configurable power supply or the power supply can directly feedback the energization time parameter, the timer collects the energization time parameter instead of timing by itself. When the energization time of the electromagnetic coil is directly set through the circuit, for example, when a capacitor is used as a power supply for discharge, the energization time of the electromagnetic coil can be adjusted by setting the circuit structure, and the timer collects the energization time of the electromagnetic coil set by the circuit structure. Correspondingly, the timer itself can be a power-on time setting module or functional component of other devices, or an independent power-on time detection and acquisition module, or a device or functional component that can acquire the power-on time parameter of other devices. When the energization time is long, the timer itself can be used for timing. Preferably, the timer can collect the energization time parameter in the configurable power supply or the power supply feedback, because when the energization time of the electromagnetic coil is very short, using the timing function of the timer itself will bring huge time error, resulting in deviation of the calculated magnetic domain wall movement speed.

[0070] More specifically, the first state is used to acquire the magnetic domain wall image under the action of the known electromagnetic coil, and calculate the movement speed of the magnetic domain wall under the action of the known electromagnetic coil according to the time data of the timer. The second state is used to acquire the magnetic domain wall image under the action of the electromagnetic coil to be calibrated, and calculate the movement speed of the magnetic domain wall under the action of the electromagnetic coil to be calibrated according to the time data of the timer. In addition, the current collection device is used to collect the current flowing into the electromagnetic coil. According to the current-magnetic field strength relationship of the known electromagnetic coil, the corresponding magnetic field strength is calculated, and according to the theoretical current-magnetic field relationship of the electromagnetic coil to be calibrated, the corresponding theoretical magnetic field strength is calculated, and then the relationship between the magnetic field strength and the magnetic domain wall movement speed of the known electromagnetic coil and the electromagnetic coil to be calibrated is compared, and the correction coefficient of the theoretical calculation value of the electromagnetic coil to be calibrated is obtained, so as to realize the calibration of the electromagnetic coil to be calibrated.

[0071] The aforementioned magnetic domain image acquisition device is a magneto-optical Kerr device, and in addition, other devices capable of imaging magnetic domains, such as a magnetic force microscope, a Lorentz microscope device, a magnetic circular dichroscope, an electron microscope device, etc., can also be used.

[0072] The application also provides another form of electromagnetic coil magnetic field strength calibration device based on magnetic domain wall motion speed ratio, comprising a magnetic domain image acquisition device, a known electromagnetic coil, a to-be-calibrated electromagnetic coil, a standard sample, a power supply, and an analysis device, wherein the magnetic domain image acquisition device acquires a magnetic domain image of the standard sample, the power supply is used to provide a preset time width and intensity of current to the known electromagnetic coil and the to-be-calibrated electromagnetic coil, and the analysis device is in communication connection with the magnetic domain image acquisition device, a current acquisition device, and the power supply.

[0073] In the first state, the known electromagnetic coil is close to the standard sample and located at a preset position, and the power supply is in electrical connection with the known electromagnetic coil.

[0074] In the second state, the to-be-calibrated electromagnetic coil is close to the standard sample and located at the preset position, and the power supply is in electrical connection with the to-be-calibrated electromagnetic coil.

[0075] It should be noted that in this case, the power supply is mainly a power supply that can be controlled by preset parameters.

[0076] The application also relates to an electromagnetic coil calibration device, which comprises a memory and a processor, the processor is used to couple with the memory, read and execute instructions in the memory, so that the calibration device realizes the aforementioned method. In addition, the application also relates to a readable storage medium, and the readable storage medium stores a computer program; the computer program is executed to realize the aforementioned method.

[0077] The basic principles, main features and advantages of the application are shown and described above, and therefore the above is only an embodiment of the application. It should be understood by those skilled in the art that the application is not limited by the above embodiment, and the above embodiment and description in the specification are only the principles of the application. Without departing from the spirit and scope of the application, various equivalent changes and improvements will fall within the scope of the claimed application.

Claims

1. An electromagnetic coil generated magnetic field strength calibration method based on magnetic domain wall motion speed ratio, characterized in that: The magnetic domain wall movement speed of a measurement sample in a magnetic field generated by a known electromagnetic coil is measured to obtain the magnetic field intensity of a measurement region; the magnetic domain wall movement speed of the measurement sample in a magnetic field generated by a to-be-calibrated electromagnetic coil is measured to calculate the magnetic field intensity of the measurement region according to a preset current-magnetic field mapping relationship of the to-be-calibrated electromagnetic coil; a calibration coefficient is calculated according to the magnetic domain wall movement speed and the magnetic field intensity, and the preset current-magnetic field mapping relationship is corrected according to the calibration coefficient.

2. The electromagnetic coil generated magnetic field strength calibration method based on magnetic domain wall motion speed ratio comparison according to claim 1, characterized in that: The magnetic domain image is obtained by one of the following methods: magneto-optical Kerr effect, magnetic force microscopy, Lorentz microscopy, magnetic circular dichroism, and electron microscopy, and the magnetic domain wall movement speed is calculated according to the magnetic domain image.

3. The electromagnetic coil generated magnetic field strength calibration method based on magnetic domain wall motion speed ratio comparison of claim 1, wherein: The magnetic domain wall movement speed is calculated by the following method: A magnetic domain image at a first time is obtained; A magnetic field excitation with a time width T is applied to the sample, and a magnetic domain image at a second time is obtained after the excitation ends; The magnetic domain wall movement speed is calculated according to the magnetic domain wall movement distance and the time width T. When measuring the magnetic domain wall movement speed, the temperature of the measurement sample when using the to-be-calibrated electromagnetic coil is the same as the temperature of the measurement sample when using the known electromagnetic coil.

4. The electromagnetic coil generated magnetic field strength calibration method based on magnetic domain wall motion speed ratio comparison of claim 1, wherein: Before calculating the magnetic domain wall movement speed, the measurement sample has uniform magnetic domains in the measurement range, a single-pulse magnetic field is generated by passing current through the electromagnetic coil to form an initial magnetic domain wall on the measurement sample.

5. The electromagnetic coil generated magnetic field strength calibration method based on magnetic domain wall motion speed ratio comparison of claim 1, wherein: The initial magnetic domain wall is circular.

6. The electromagnetic coil generated magnetic field strength calibration method based on magnetic domain wall motion speed ratio comparison of claim 5, wherein: The magnetic domain wall of the measurement sample is driven by passing current through the electromagnetic coil to generate a single-pulse magnetic field.

7. The electromagnetic coil generated magnetic field strength calibration method based on magnetic domain wall motion speed ratio comparison of claim 1, wherein: The magnetic domain image is obtained by magneto-optical Kerr effect, and the axis of the electromagnetic coil is located in a light spot region where the magneto-optical Kerr effect is generated.

8. The electromagnetic coil generated magnetic field strength calibration method based on magnetic domain wall motion speed ratio comparison of claim 1, wherein: The range of the measurement region for calculating the magnetic domain wall movement speed is included in the range of the light spot region where the magneto-optical Kerr effect is generated.

9. The electromagnetic coil generated magnetic field strength calibration method based on magnetic domain wall motion speed ratio comparison of claim 8, wherein: The magnetic field B2 generated by the to-be-calibrated electromagnetic coil is a0a2I, where I is the current passing through the to-be-calibrated electromagnetic coil, and a0 is a preset current-magnetic field mapping parameter of the to-be-calibrated electromagnetic coil.

10. The electromagnetic coil generated magnetic field strength calibration method based on magnetic domain wall motion speed ratio comparison of claim 1, wherein: Measuring the magnetic domain wall motion velocity v1 in the magnetic field generated by the known electromagnetic coil, recording the corresponding magnetic field strength H1, obtaining multiple sets of v1, H1, fitting H1 -1 / 4 The linear relationship between Inv1 and H1, obtaining the intercept b1 and the slope k1 of the linear relationship. Measuring the domain wall motion speed v2 in the magnetic field generated by the electromagnetic coil to be calibrated, calculating the magnetic field intensity of the measurement region according to the preset current magnetic field mapping relationship, recording the corresponding magnetic field intensity H2, obtaining a plurality of groups of quantities v2, H2, fitting H2 -1 / 4 The linear relationship between Inv2 and H2, the intercept b2 and the slope k2 of the linear relationship are obtained. The calibration coefficient is a2 = (k1 / k2) 4 .

11. The electromagnetic coil generated magnetic field strength calibration method based on magnetic domain wall motion speed ratio comparison of claim 10, wherein: The magnetic domain image is obtained by magneto-optical Kerr effect, and the magneto-optical Kerr effect at least includes polar magneto-optical Kerr effect, and the electromagnetic coil generates a vertical magnetic field at least in the measurement region of the measurement sample, and the vertical magnetic field at least has a magnetic field component perpendicular to the measured surface of the measurement sample.

12. The electromagnetic coil generated magnetic field strength calibration method based on magnetic domain wall motion speed ratio comparison of claim 10, wherein: If b2≠b1, re-adjust the position of the electromagnetic coil to be calibrated, re-acquire v2, H2, and use the re-acquired v2, H2 to fit H2 -1 / 4 a linear relationship between Inv2 and Inv1 and acquire b2, k2 until b2=b1.

13. The method for calibrating the magnetic field strength of an electromagnetic coil based on the comparison of magnetic domain wall motion velocities as described in claim 1, characterized in that: The device comprises a magnetic domain image acquisition device, a current acquisition device, a known electromagnetic coil, a to-be-calibrated electromagnetic coil, a measurement sample, a power supply, a timer, and an analysis device, the magnetic domain image acquisition device acquires the magnetic domain image of the measurement sample, the timer is used to acquire the energization time of the electromagnetic coil, and the analysis device is in communication connection with the magnetic domain image acquisition device, the current acquisition device, and the timer; 14. An electromagnetic coil generated magnetic field strength calibration device based on magnetic domain wall motion speed ratio, characterized in that: In a first state, the known electromagnetic coil is close to the measurement sample and located at a preset position, the power supply is electrically connected with the known electromagnetic coil, and the current acquisition device is used to measure the current value passing through the known electromagnetic coil. ​ In the second state, the electromagnetic coil to be calibrated is close to the standard sample and located at the preset position, the power supply is electrically connected with the electromagnetic coil to be calibrated, and the current acquisition device is used to measure the current value of the known electromagnetic coil.

15. The magnetic field strength calibration device based on the speed ratio of magnetic domain wall motion of claim 14, wherein: The magnetic domain image acquisition device is at least one of a magneto-optical Kerr device, a magnetic force microscope, a Lorentz microscope device, a magnetic circular dichroism mirror, and an electron microscope device.

16. An electromagnetic coil generated magnetic field strength calibration device based on magnetic domain wall motion speed ratio, characterized in that: The magnetic domain image acquisition device, the known electromagnetic coil, the electromagnetic coil to be calibrated, the standard sample, the power supply, and the analysis device are included. The magnetic domain image acquisition device acquires a magnetic domain image of the standard sample. The power supply is used to provide a preset time width and intensity of current to the known electromagnetic coil and the electromagnetic coil to be calibrated. The analysis device is in communication connection with the magnetic domain image acquisition device, the current acquisition device, and the power supply. In the first state, the known electromagnetic coil is close to the standard sample and located at the preset position, and the power supply is electrically connected with the known electromagnetic coil. In the second state, the electromagnetic coil to be calibrated is close to the standard sample and located at the preset position, and the power supply is electrically connected with the electromagnetic coil to be calibrated.

17. An electromagnetic coil calibration apparatus, characterized by: The calibration device includes a memory and a processor. The processor is used to read and execute instructions in the memory, so that the calibration device implements the method in any one of claims 1-13.

18. A readable storage medium characterized by: The computer program is stored on the readable storage medium and is executed to implement the method in any one of claims 1-13.

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