Pulsed magnetic measurement device and method

Abstract

The present application relates to a pulse magnetic measurement device and method. A pulse magnetic measurement method comprises: generating a preset pulse magnetic field to place the magnetization of a sample in a predetermined direction; generating a first reverse pulse magnetic field opposite to the direction of the preset pulse magnetic field, and measuring the magnetic field strength H value of the first reverse pulse magnetic field and the magnetic polarization strength J value of the sample in the first reverse pulse magnetic field, to obtain a first reverse JH relationship curve; generating a second same direction pulse magnetic field same as the direction of the first reverse pulse magnetic field, and measuring the magnetic field strength H value of the second same direction pulse magnetic field and the magnetic polarization strength J value of the sample in the second same direction pulse magnetic field, to obtain a second same direction JH relationship curve; subtracting the magnetic polarization strength J value corresponding to the same magnetic field strength H value in the first reverse JH relationship curve and the second same direction JH relationship curve, to obtain a relationship curve of the difference value of the magnetic polarization strength J value and the corresponding magnetic field strength H value as a first half-axis magnetic hysteresis loop of the sample.

Description

Technical Field

[0001] This invention relates generally to the field of magnetic measurement technology, and more particularly to a pulse magnetic measurement device and method. Background Technology

[0002] Pulsed magnetic field measurement is a common method for measuring the hysteresis loop (J(H) relationship curve or B(H) relationship curve, also known as the saturation demagnetization curve) of magnetic samples, especially those with high coercivity, such as permanent magnet materials. Many magnetic parameters of magnetic samples, such as saturation magnetization, remanent magnetization, coercivity, energy product, and squareness of the demagnetization curve, can be measured on the hysteresis loop. The basic principle of pulsed magnetic field measurement is to use a strong pulsed magnetic field generated by a magnetic field generator to magnetize the sample, record and process the magnetic field strength and the sample's magnetization state, thereby obtaining the hysteresis loop. Pulsed magnetic field generators made of conventional conductive materials can achieve high magnetic fields of up to 16,000–24,000 kA / m by limiting the pulse width. This is significantly cheaper than the cost of obtaining a 4,000 kA / m magnetic field using a superconducting magnetization device, thus meeting the magnetic measurement needs of high coercivity samples at a lower cost.

[0003] However, current pulsed magnetic field measurement techniques still have many problems that affect measurement accuracy. For example, due to the dynamic effects induced by the pulsed magnetic field, eddy currents generated inside the sample produce additional magnetic fields, affecting the measured magnetization intensity. Furthermore, the sample shape affects the demagnetization factor, leading to differences in the measured demagnetization field. These factors influence the measurement results and prevent them from fully reflecting the intrinsic properties of the material.

[0004] Therefore, further improvements are still needed to the pulse magnetism measurement technology in order to continuously improve measurement accuracy. Summary of the Invention

[0005] One aspect of this application provides a pulsed magnetic field measuring device, comprising: an excitation coil for generating a pulsed magnetic field; a capacitor bank for applying current to the excitation coil to generate the pulsed magnetic field; a pulse commutation module for controlling the direction of the current applied by the capacitor bank to the excitation coil to generate a positive or negative pulsed magnetic field; a measuring coil including an H coil for measuring the magnetic field strength H of the pulsed magnetic field and a J coil for measuring the magnetic polarization J of a sample in the pulsed magnetic field; a first integrator for integrating the voltage signal output by the H coil over time to obtain an H signal representing the magnetic field strength H of the pulsed magnetic field; a second integrator for integrating the voltage signal output by the J coil over time to obtain a J signal representing the magnetic polarization J of the sample; an analog-to-digital converter for converting the H signal and the J signal from analog signals into digital signals; and a data processing unit for performing signal processing on the converted digital H signal and the J signal to obtain a JH relationship curve of the sample. Under the control of the pulse commutation module, the excitation coil first generates a preset pulse magnetic field to magnetize the sample in a predetermined direction; then, it generates a first reverse pulse magnetic field opposite to the preset pulse magnetic field to measure the first reverse JH relationship curve of the sample; then, it generates a second co-directional pulse magnetic field in the same direction as the first reverse pulse magnetic field to measure the second co-directional JH relationship curve of the sample. The data processing unit subtracts the magnetic polarization intensity J values ​​corresponding to the same magnetic field strength H value from the first reverse JH relationship curve and the second co-directional JH relationship curve to obtain the relationship curve between the difference in magnetic polarization intensity J value and the corresponding magnetic field strength H value, which serves as the first half-axis hysteresis loop of the sample.

[0006] In one embodiment, the data processing unit further determines a symmetrical second half-axis hysteresis loop based on the first half-axis hysteresis loop, thereby obtaining the complete hysteresis loop of the sample, wherein the first half-axis hysteresis loop and the second half-axis hysteresis loop correspond to one and the other of the positive and negative half-axis of the magnetic field strength H value, respectively.

[0007] In one embodiment, under the control of the pulse commutation module, the excitation coil also generates a third reverse pulse magnetic field opposite to the direction of the second co-directional pulse magnetic field to measure the third reverse JH relationship curve of the sample; then, it generates a fourth co-directional pulse magnetic field in the same direction as the third reverse pulse magnetic field to measure the fourth co-directional JH relationship curve of the sample. The data processing unit also subtracts the magnetic polarization J values ​​corresponding to the same magnetic field strength H value from the third reverse JH relationship curve and the fourth co-directional JH relationship curve to obtain the relationship curve between the difference in magnetic polarization J value and the corresponding magnetic field strength H value, which serves as the second half-axis hysteresis loop of the sample, thereby obtaining the complete hysteresis loop of the sample. The first half-axis hysteresis loop and the second half-axis hysteresis loop correspond to one and the other of the positive and negative half-axis of the magnetic field strength H value, respectively.

[0008] In one embodiment, the first reverse pulse magnetic field and the second co-directional pulse magnetic field have the same pulse width, amplitude, and shape, the third reverse pulse magnetic field and the fourth co-directional pulse magnetic field have the same pulse width, amplitude, and shape, and the third reverse pulse magnetic field and the fourth co-directional pulse magnetic field have pulse widths different from those of the first reverse pulse magnetic field and the second co-directional pulse magnetic field.

[0009] In one embodiment, the sample is cylindrical and has an aspect ratio in the range of 1.125 ± 5%.

[0010] Another aspect of this application provides a pulsed magnetic field measurement method, comprising: generating a preset pulsed magnetic field to magnetize a sample in a predetermined direction; generating a first reverse pulsed magnetic field opposite to the direction of the preset pulsed magnetic field, and measuring the magnetic field strength H of the first reverse pulsed magnetic field and the magnetic polarization J of the sample in the first reverse pulsed magnetic field to obtain a first reverse JH relationship curve; generating a second co-directional pulsed magnetic field in the same direction as the first reverse pulsed magnetic field, and measuring the magnetic field strength H of the second co-directional pulsed magnetic field and the magnetic polarization J of the sample in the second co-directional pulsed magnetic field to obtain a second co-directional JH relationship curve; subtracting the magnetic polarization J values ​​corresponding to the same magnetic field strength H values ​​from the first reverse JH relationship curve and the second co-directional JH relationship curve to obtain a relationship curve between the difference in magnetic polarization J values ​​and the corresponding magnetic field strength H values, which serves as the first half-axis hysteresis loop of the sample.

[0011] In one embodiment, the pulsed magnetic measurement method further includes: determining a symmetrical second half-axis hysteresis loop based on the first half-axis hysteresis loop, thereby obtaining the complete hysteresis loop of the sample, wherein the first half-axis hysteresis loop and the second half-axis hysteresis loop correspond to one and the other of the positive and negative half-axis of the magnetic field strength H value, respectively.

[0012] In one embodiment, the pulsed magnetic measurement method further includes: generating a third reverse pulsed magnetic field opposite in direction to the second co-directional pulsed magnetic field, and measuring the magnetic field strength H of the third reverse pulsed magnetic field and the magnetic polarization J of the sample in the third reverse pulsed magnetic field to obtain a third reverse JH relationship curve; generating a fourth co-directional pulsed magnetic field in the same direction as the third reverse pulsed magnetic field, and measuring the magnetic field strength H of the fourth co-directional pulsed magnetic field and the magnetic polarization J of the sample in the fourth co-directional pulsed magnetic field to obtain a fourth co-directional JH relationship curve; subtracting the magnetic polarization J corresponding to the same magnetic field strength H in the third reverse JH relationship curve and the fourth co-directional JH relationship curve to obtain a relationship curve between the difference in magnetic polarization J and the corresponding magnetic field strength H, which serves as the second half-axis hysteresis loop of the sample, thereby obtaining the complete hysteresis loop of the sample. The first half-axis hysteresis loop and the second half-axis hysteresis loop correspond to one and the other of the positive and negative half-axis of the magnetic field strength H, respectively.

[0013] In one embodiment, the first reverse pulse magnetic field and the second co-directional pulse magnetic field have the same pulse width, amplitude, and shape, the third reverse pulse magnetic field and the fourth co-directional pulse magnetic field have the same pulse width, amplitude, and shape, and the third reverse pulse magnetic field and the fourth co-directional pulse magnetic field have pulse widths different from those of the first reverse pulse magnetic field and the second co-directional pulse magnetic field.

[0014] In one embodiment, the sample is cylindrical and has an aspect ratio in the range of 1.125 ± 5%.

[0015] The above and other features and advantages of the present invention will become apparent from the following description of specific embodiments taken in conjunction with the accompanying drawings. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of a pulse magnetic measurement device according to an embodiment of the present invention.

[0017] Figure 2 yes Figure 1 The diagram shows the trigger signal and corresponding pulse waveform of the semiconductor control module 114 in the pulsed magnetic measurement device.

[0018] Figure 3 This is a schematic diagram of the pulsed magnetic field used in the pulsed magnetic measurement process according to an embodiment of the present invention.

[0019] Figure 4 This is a schematic diagram of half of the hysteresis loop obtained by using a positive pulse measurement during a pulse magnetic measurement process according to an embodiment of the present invention.

[0020] Figure 5 This is a schematic diagram of a complete hysteresis loop obtained by measuring positive and negative pulses during a pulsed magnetic measurement process according to an embodiment of the present invention.

[0021] Figure 6 This is a schematic diagram of the magnetic field lines of a cylindrical sample.

[0022] Figure 7 This is a graph showing the relationship between the aspect ratio and demagnetization factor of a cylindrical sample under different magnetic susceptibility (or permeability).

[0023] Figure 8 This is a flowchart of a pulse magnetism measurement method according to an embodiment of the present invention. Detailed Implementation

[0024] Hereinafter, exemplary embodiments according to this application will be described in detail with reference to the accompanying drawings. Note that the drawings may not be drawn to scale. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments of this application, and this application is not limited to the exemplary embodiments described herein.

[0025] Figure 1 This is a schematic diagram of a pulse magnetic measurement device 100 according to an embodiment of the present invention. Figure 1 The pulse magnetic measurement device 100 shown uses some of the same components or modules as existing pulse magnetic measurement devices, which will be briefly described below, while the differences between the pulse magnetic measurement device 100 of the present invention and the prior art will be highlighted.

[0026] Reference Figure 1 The pulse magnetic measurement device 100 includes a power supply module 110, a capacitor bank 112, a semiconductor control module 114, a pulse commutation module 130, and an excitation coil 116.

[0027] The power supply module 110 can be connected to an external power source to charge the capacitor bank 112. During charging, the switch 101 is turned on, and the semiconductor control module 114 is turned off. The semiconductor control module 114 can be, for example, a bidirectional dual thyristor. The capacitor bank 112 can be charged for a relatively long time, allowing electrical energy to accumulate in the capacitor bank 112.

[0028] After the capacitor bank 112 is fully charged, switch 101 is opened, and a trigger signal is synchronously sent to the forward and reverse thyristors in the semiconductor control module 114. Both thyristors turn on simultaneously, and the capacitor bank 112 begins to discharge, generating a pulsed magnetic field in the excitation coil 116. The capacitor bank 112 can complete its discharge in a relatively short time, generating a high current, which in turn causes the excitation coil 116 to generate a large pulsed magnetic field. When the capacitor bank 112 has finished discharging, the excitation coil 116 generates a sinusoidal pulsed magnetic field of half a cycle (i.e., 0-180°), which can also be called a half-wave (i.e., half a wavelength, relative to a complete cycle of a sine curve) pulse. Energy accumulates in the excitation coil 116 at this time.

[0029] like Figure 2 As shown in small figure (a), when the pulse width of the trigger signal applied to the semiconductor control module 114 is greater than 180° (i.e., greater than 180° but less than 360°), the discharge current (or reverse charging current) of the excitation coil 116 can be conducted through the reverse thyristor to reverse charge the capacitor bank 112. This allows the forward and reverse circuits to conduct continuously, generating a 360° sinusoidal pulse waveform. The electrical energy dissipated by the coil during the discharge half-cycle will be restored in the capacitor bank 112 for use in the next capacitor discharge.

[0030] In one embodiment of the present invention, such as Figure 2 As shown in small figure (b), the pulse width of the trigger signal applied to the semiconductor control module 114 can be less than 180° (i.e., greater than 0° and less than 180°). Therefore, after generating a sinusoidal half-wave (0°-180°) pulse, the excitation coil 116 cannot reverse charge the capacitor bank 112. At this time, the semiconductor control module 114 acts as a large resistor for the reverse charging current, causing the energy stored in the excitation coil 116 to dissipate quickly, preventing the generation of an inverted half-wave (180°-360°) pulse. When the power supply module 110 charges the capacitor bank 112 again, the pulse commutation module 130 can be used to change the direction of the current applied from the capacitor bank 112 to the excitation coil 116, thereby obtaining an inverted (negative) half-wave pulse with equal amplitude. The pulse commutation module 130 can be implemented as, for example, a relay, which, under the control of a control signal, applies the discharge current of the capacitor bank 112 to the excitation coil 116 in either the forward or reverse direction. Figure 1 As shown.

[0031] It is understood that the pulse discharge circuit including the semiconductor control module 114 shown herein is merely an example, and other pulse discharge modules in the prior art can also be used to achieve the desired pulsed magnetic field, such as the half-wave (i.e., half-wavelength) pulsed magnetic field used in this invention.

[0032] On the measurement side, the pulsed magnetic measurement device 100 may include a measurement coil 118, a J-channel integrator 120a, an H-channel integrator 120b, an analog-to-digital converter (ADC) 122, and a data processing unit 124. The measurement coil 118 may include a magnetic polarization measurement coil (referred to as the J coil) and a magnetic field strength measurement coil (referred to as the H coil), which are used to measure the magnetic polarization J of the sample 102 and the magnetic field strength H at the location of the sample 102 (i.e., the magnetic field strength generated by the excitation coil 106), respectively. In the CGS unit system (i.e., centimeter-gram-second unit system), the value of the magnetic polarization J of the sample is equal to the magnetization M; therefore, magnetic polarization and magnetization are used interchangeably herein. The J coil and H coil may employ coil structures commonly used in the art, and the H coil may be placed on the same structure as the J coil. For clarity, the excitation coil 116, measuring coil 118, and sample 102 are shown separately. However, it should be understood that during measurement, the measuring coil 118 may be located within the excitation coil 116, and the sample 102 may be located at the center of the measuring coil 118. The sample 102 can be a sample of any magnetic material. In some embodiments, for ease of demonstration of the principles of the invention, the sample 102 may be a permanent magnet sample with high coercivity, and the sample 102 may be prepared in a cylindrical shape with a length h to diameter D ratio (length-to-diameter ratio) in the range of 1.125 ± 5%.

[0033] The output signal of test coil 118 is proportional to the derivative of the induced magnetic flux with respect to time, where the output voltage U of coil H is... H and the output voltage U of coil J J It can be expressed by the following formulas (1) and (2):

[0034]

[0035]

[0036] The J-channel integrator 120a and H-channel integrator 120b can respectively measure the output voltage U of the J-coil and H-coil. J and U H Integration is performed to obtain J and H signals. The obtained J and H signals are converted into digital signals by an analog-to-digital converter (ADC) 122 to obtain the raw data of the measurement results, namely the measured magnetic polarization J value and magnetic field strength H value. The data processing unit 124 processes the raw measurement results, including, for example, removing "zero signals", centering the hysteresis loop, and noise reduction filtering, to obtain the measurement results of J and H, that is, the JH relationship curve, or the J(H) hysteresis loop, which can be further converted to obtain the B(H) hysteresis loop.

[0037] The basic principle of pulsed magnetic field measurement has been described above. However, as mentioned earlier, the eddy currents generated inside the sample during measurement, and the influence of the sample shape on the demagnetization factor, will affect the measurement results, thereby reducing the measurement accuracy and causing the results to not accurately reflect the intrinsic properties of the material itself. Below, we will refer to... Figure 3-5 A pulsed magnetic measurement method according to an embodiment of the present invention is described, which can reduce or eliminate the influence of sample eddy currents on the measurement results.

[0038] First refer to Figure 3 This diagram illustrates a pulsed magnetic field used in a pulsed magnetic measurement process according to an embodiment of the present invention. It should be understood that the pulse shape here is only schematic and can be, for example, a sinusoidal pulse or other desired pulse shape.

[0039] like Figure 3 As shown, initially, an initial pulsed magnetic field 201 (hereinafter, the pulsed magnetic field can also be simply referred to as a pulse) can be generated using the excitation coil 116. This can also be called a preset pulse, used to magnetize the sample in a predetermined initial direction. For ease of description, the preset pulse 201 is shown as a negative pulse here, but it should be understood that it can also be a positive pulse. In this application, positive and negative are only relative, representing two opposite magnetization directions or waveform phases. The positive pulse described in this application can also be a negative pulse, and vice versa.

[0040] Then, the excitation coil 116 can generate a forward-reverse (or anti-phase) pulse 203. Here, "reverse / anti-phase" refers to the previous pulse (for pulse 203, the previous pulse is the preset pulse 201), and its magnetic field direction is opposite. As mentioned earlier, the direction of the current applied to the excitation coil 116 can be controlled using the pulse commutation module 130, thereby obtaining a pulsed magnetic field in the desired direction. Using the forward-reverse pulse 203, the magnetic polarization intensity (J signal) of sample 102 and the magnetic field intensity (H signal) of sample 102 can be measured to obtain the forward-reverse JH relationship curve, which is half of the complete hysteresis loop, that is, half of the hysteresis loop corresponding to the positive half-axis of H, as shown below. Figure 4 The curve with a circle in the middle is shown.

[0041] Next, the excitation coil 116 can generate a positive in-phase (or co-directional) pulse 205. Here, because pulse 205 has the same direction (phase) as the previous pulse 203, both being positive, pulse 205 is called a positive in-phase pulse. Using the positive in-phase pulse 205, the magnetic polarization intensity (J signal) of sample 102 and the magnetic field intensity (H signal) of sample 102 can be measured, obtaining a positive in-phase (i.e., non-anti-phase) JH relationship curve, which is half of the hysteresis loop corresponding to the positive half-axis of H, as shown below. Figure 4The curve with a square in the middle is shown.

[0042] Then, the data processing unit 124 can subtract the two magnetic polarization intensities J values ​​corresponding to the same magnetic field strength H value from the forward-anti-phase JH relationship curve and the forward-in-phase JH relationship curve to obtain the relationship curve between the difference in magnetic polarization intensities J values ​​and the corresponding magnetic field strength H value, as the hysteresis loop measurement result of the positive half-axis of H, such as... Figure 4 The curve with the triangle is shown in the diagram. When performing the subtraction operation, interpolation can be performed if necessary to obtain the same H value and corresponding J value, thus allowing the subtraction of two J values ​​corresponding to the same H value. It can be understood that because the initial states of the two positive pulses 203 and 205 are different, there is a difference between the measured magnetic moment reversal and non-reversal J values. Therefore, when subtracting them, the difference can represent the signal of the magnetic moment reversal process when the external field (i.e., the H signal) changes. On the other hand, when the change process of the external magnetic field is the same, the eddy currents generated in sample 102 can be considered the same. Therefore, the influence of eddy currents on the magnetic polarization measurement results can be removed through the subtraction operation, thereby improving the measurement accuracy. It can be understood that pulses 203 and 205 have the same width, amplitude, shape, etc.

[0043] The above measurements using pulses 201, 203, and 205 yielded a half-hysteresis loop corresponding to the positive half-axis of the H signal. Since the hysteresis loops of magnetic materials generally exhibit symmetry, the data processing unit 124 can obtain a symmetrical negative half-axis hysteresis loop based on the positive half-axis hysteresis loop obtained above, thus obtaining the complete hysteresis loop. Figure 4 (Not shown in the image).

[0044] In another embodiment, the same principle can be used to continue measuring and obtaining the hysteresis loop corresponding to the negative half-axis of the magnetic field strength H. Specifically, as... Figure 3 As shown, the excitation coil 116 can generate a negative anti-phase pulse 207. Here, the magnetic field direction of pulse 207 is opposite to that of the previous pulse 205. That is, pulse 205 can be regarded as the preset pulse for measurement corresponding to pulse 207, which presets the magnetization of sample 102 to the desired direction. As mentioned earlier, the direction of the current applied to the excitation coil 116 can be controlled by the pulse commutation module 130 to obtain the pulsed magnetic field in the desired direction. The negative anti-phase pulse 207 can be used to measure the magnetic polarization intensity (J signal) of sample 102 and the magnetic field intensity (H signal) of sample 102, obtaining the negative anti-phase JH relationship curve, which is half of the hysteresis loop corresponding to the negative half axis of H. Figure 5 As shown in the image. Figure 5 The circled curve represents the complete antiphase hysteresis loop (corresponding to the positive and negative half-axis of H) obtained by measuring with pulses 203 and 207.

[0045] Next, the excitation coil 116 can generate a negative in-phase (or in-phase) pulse 209. Here, because pulse 209 has the same direction (phase) as the previous pulse 207, both being negative, pulse 209 is called a negative in-phase pulse. It can be understood that pulses 207 and 209 can have the same width, amplitude, shape, etc. In one embodiment, pulses 207 and 209 can have the same amplitude as pulses 203 and 205. Using the negative in-phase pulse 209, the magnetic polarization intensity (J signal) of sample 102 and the magnetic field intensity (H signal) of sample 102 can be measured, obtaining a negative in-phase (i.e., non-anti-phase) JH relationship curve, which is half of the hysteresis loop corresponding to the negative half-axis of H. Figure 5 As shown in the image. Figure 5 The curve with squares in the figure represents the complete in-phase (non-out-of-phase) hysteresis loop obtained by measuring with pulses 205 and 209 (corresponding to the positive and negative half-axis of H).

[0046] Then, the data processing unit 124 can subtract the two magnetic polarization intensities J values ​​corresponding to the same magnetic field strength H value from the negative anti-phase JH relationship curve and the negative in-phase (non-anti-phase) JH relationship curve to obtain the relationship curve formed by the difference in magnetic polarization intensities J value and the corresponding magnetic field strength H value, as the hysteresis loop measurement result of the negative half-axis of H, such as... Figure 5 As shown in the image. Figure 5 The curve with triangles represents the complete hysteresis loop (corresponding to the positive and negative half-axis of H) obtained by the difference.

[0047] As mentioned earlier, the measurement results of the positive double pulses (203 and 205) and the negative double pulses (207 and 209) exhibit a certain degree of symmetry. In one embodiment, to obtain more favorable dynamic information for inversion during testing, the width of the negative pulse can be set differently from that of the positive pulse; for example, the negative pulse can be wider than the positive pulse, with a pulse width ratio of 2:1, to achieve more accurate inversion. For instance, if symmetrical measurement results are obtained using different pulse widths, the measurement results can be determined to be accurate; conversely, if asymmetrical measurement results are obtained using different pulse widths, it indicates that the measurement process may be affected by some unknown factor and may be inaccurate. Moreover, using different positive and negative pulse widths also helps to provide more refined eddy current subtraction process information, i.e., subtracting the influence of eddy currents while retaining the intrinsic magnetization properties of sample 102.

[0048] The above reference Figure 3 Pulses 201 to 209 are described as positive or negative pulses, but it should be understood that pulses 201, 205 and 209 can also be positive pulses, and pulses 203 and 205 can also be negative pulses, which are equally applicable to the principles of the invention described above.

[0049] from Figure 4 and Figure 5 The measurement results show that, in both anti-phase and non-anti-phase (i.e., in-phase) measurements, the magnetic polarization of sample 102 increases with increasing magnetic field strength. This is believed to be due to the influence of eddy currents, as a greater change in magnetic flux results in a larger eddy current generated in sample 102. The influence of the eddy current magnetic field leads to a greater measured magnetic polarization of sample 102, but this measurement result does not conform to the saturation magnetization property of permanent magnet sample 102. However, the hysteresis loop obtained by using the difference between anti-phase and non-anti-phase (i.e., in-phase) measurements exhibits flat saturation magnetization, which matches the saturation magnetization property of permanent magnet sample 102. Therefore, this result eliminates the influence of sample eddy currents and has higher measurement accuracy.

[0050] As mentioned earlier, the shape of sample 102 affects the demagnetization factor, and thus the results of magnetic measurements. Theoretically, an isotropic spherical sample possesses high symmetry, and the demagnetization factor is the same at all points within the sample. However, it is difficult to fabricate a spherical sample, or it would incur higher costs. Alternatively, sample 102 can be prepared in a cylindrical shape. Figure 6 The distribution of magnetic field lines in a cylindrical sample is shown. At the middle of the sample, the magnetic field lines appear to be basically parallel and uniform. However, at both ends of the sample, the magnetic field lines diverge outwards. It can be seen that the magnetic field lines in the sample are not parallel and uniform. In other words, the demagnetization factor at different points in the sample is not the same. It is evident that the sample shape affects the demagnetization factor, which in turn causes the magnetic polarization intensity of the sample measured by the J coil to be affected by the demagnetization field and thus produce deviation.

[0051] To reduce the influence of the sample demagnetizing field on the measurement results, the inventors investigated the relationship between sample shape and demagnetizing factor. Here, the sample is prepared as a cylinder, the shape of which can be represented by the aspect ratio γ = h / D. When the magnetic susceptibility (or permeability, since permeability = susceptibility + 1) of the sample is determined, the demagnetizing factor N at the center of the sample can be calculated based on the sample shape. f The results are shown in Figure 7 In the middle. For example Figure 7 As shown, for magnetic susceptibility from 0 to 999 (or permeability from 1 to 1000), the demagnetization factor N in the middle of the sample is... f It varies linearly with the sample shape, specifically the aspect ratio of a cylindrical sample. Figure 7 It can be determined that when the aspect ratio γ is around 1.125, the demagnetization factor N varies for different magnetic susceptibility. f The variation is within ±0.3%, therefore the demagnetization factor N can be considered to be within a certain range. fIt is essentially constant and does not change with the magnetic susceptibility of the sample. In some embodiments of the invention, the aspect ratio γ can be set within the range of 1.125 ± 5%, such as... Figure 7 As shown, the demagnetizing factor N is within this range. f The variation range is approximately ±1%, which can be considered as the demagnetization factor N. f Basically, there is no change, or the change is so small that its impact on the accuracy of magnetic measurements is negligible.

[0052] Figure 8 This is a flowchart of a pulse magnetism measurement method 200 according to an embodiment of the present invention. Method 200 can utilize... Figure 1 The magnetic pulse measurement device 100 shown is used to perform this operation. Figure 8 As shown, method 200 may include step 210, generating a preset pulsed magnetic field, for example... Figure 3 The pulsed magnetic field 201 shown is used to magnetize the sample 102 in a predetermined direction; step 212 generates a first reverse pulsed magnetic field with the opposite direction to the preset pulsed magnetic field 201, for example... Figure 3 The pulsed magnetic field 203 is shown, and the magnetic field strength H value of the first reverse pulsed magnetic field 203 and the magnetic polarization intensity J value of sample 102 in the first reverse pulsed magnetic field 203 are measured to obtain the first reverse JH relationship curve; step 214, a second pulsed magnetic field with the same direction as the first reverse pulsed magnetic field 203 is generated, for example Figure 3 The pulsed magnetic field 205 is shown, and the magnetic field strength H value of the second co-directional pulsed magnetic field 205 and the magnetic polarization intensity J value of the sample 102 in the second co-directional pulsed magnetic field 205 are measured to obtain the second co-directional JH relationship curve; and in step 216, the magnetic polarization intensity J value corresponding to the same magnetic field strength H value in the first reverse JH relationship curve and the second co-directional JH relationship curve is subtracted to obtain the difference of magnetic polarization intensity J value and the corresponding magnetic field strength H value, which is used as the first half-axis hysteresis loop of the sample 102.

[0053] Optionally, in step 218, a symmetrical second half-axis hysteresis loop can also be determined based on the first half-axis hysteresis loop, thereby obtaining the complete hysteresis loop of the sample. It can be understood that the first and second half-axis hysteresis loops correspond to one and the other of the positive and negative half-axis of the magnetic field strength H, respectively. Then, method 200 ends.

[0054] Optionally, in another embodiment, method 200 may further include step 220, generating a third reverse pulsed magnetic field opposite in direction to the second unidirectional pulsed magnetic field 205, for example... Figure 3The pulsed magnetic field 207 is shown, and the magnetic field strength H value of the third reverse pulsed magnetic field 207 and the magnetic polarization intensity J value of sample 102 in the third reverse pulsed magnetic field 207 are measured to obtain the third reverse JH relationship curve; step 222, a fourth pulsed magnetic field with the same direction as the third reverse pulsed magnetic field 207 is generated, for example Figure 3 The pulsed magnetic field 209 is shown, and the magnetic field strength H value of the fourth co-directional pulsed magnetic field 209 and the magnetic polarization intensity J value of sample 102 in the fourth co-directional pulsed magnetic field 209 are measured to obtain the fourth co-directional JH relationship curve; then in step 224, the magnetic polarization intensity J value corresponding to the same magnetic field strength H value in the third reverse JH relationship curve and the fourth co-directional JH relationship curve are subtracted to obtain the difference in magnetic polarization intensity J value and the corresponding magnetic field strength H value, which is used as the second half-axis hysteresis loop of sample 102, thereby obtaining the complete hysteresis loop of sample 102. It can be understood that the first half-axis hysteresis loop and the second half-axis hysteresis loop correspond to one and the other of the positive and negative half-axis of the magnetic field strength H value, respectively.

[0055] In method 200 described above, sample 102 can be formed into a cylindrical shape, and the aspect ratio γ of the cylinder can be set in the range of 1.125 ± 5%. This ensures that the demagnetization factor of sample 102 remains essentially unchanged with respect to the magnetic susceptibility / permeability of the sample, or that the change is minimal, thereby reducing or essentially eliminating the influence of the sample's demagnetizing field on the accuracy of magnetic measurements.

[0056] The basic principles of this application have been described above with reference to specific embodiments. However, it should be noted that the advantages, benefits, and effects mentioned in this application are merely examples and not limitations, and should not be considered as essential features of each embodiment of this application. Furthermore, the specific details disclosed above are for illustrative and facilitative purposes only, and are not limitations. These details do not limit the application to the necessity of employing the aforementioned specific details for implementation.

[0057] The block diagrams of devices, apparatuses, devices, and systems involved in this application are merely illustrative examples and are not intended to require or imply that they must be connected, arranged, or configured in the manner shown in the block diagrams. As those skilled in the art will recognize, these devices, apparatuses, devices, and systems can be connected, arranged, and configured in any manner. Each block shown in the figures can be subdivided into multiple sub-blocks, each sub-block implementing a related function or step, so that multiple sub-blocks can achieve the function implemented by a larger block before subdivision. Alternatively, multiple blocks shown in the figures can also be combined into a single block, which can achieve the functions of the multiple blocks before merging. In this application, words such as "comprising," "including," "having," etc., are open-ended terms meaning "including but not limited to," and are used interchangeably with them. The terms "or" and "and" as used herein refer to the terms "and / or," and are used interchangeably with them unless the context clearly indicates otherwise. The term "such as" as used herein refers to the phrase "such as but not limited to," and is used interchangeably with it.

[0058] It should be noted that in the apparatus, equipment, and methods of this application, the components or steps can be disassembled and / or recombined. These disassemblies and / or recombinations should be considered as equivalent solutions of this application.

[0059] The above description of the disclosed aspects is provided to enable any person skilled in the art to make or use this application. Various modifications to these aspects will be readily apparent to those skilled in the art, and the general principles defined herein can be applied to other aspects without departing from the scope of this application. Therefore, this application is not intended to be limited to the aspects shown herein, but rather to be accorded the widest scope consistent with the principles and novel features disclosed herein.

[0060] The above description has been given for purposes of illustration and description. Furthermore, this description is not intended to limit the embodiments of this application to the forms disclosed herein. Although numerous exemplary aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, alterations, additions, and sub-combinations thereof.

Claims

1. A pulse magnetic measurement device, comprising: Excitation coils are used to generate pulsed magnetic fields; A capacitor bank is used to apply current to the excitation coil to generate the pulsed magnetic field; A pulse commutation module is used to control the direction of the current applied by the capacitor bank to the excitation coil in order to generate a positive pulse magnetic field or a negative pulse magnetic field. The measuring coil includes an H coil for measuring the magnetic field strength H of the pulsed magnetic field and a J coil for measuring the magnetic polarization J of the sample in the pulsed magnetic field. The first integrator is used to integrate the voltage signal output by the H coil over time to obtain the H signal representing the magnetic field strength H of the pulsed magnetic field. The second integrator is used to integrate the voltage signal output by the J coil over time to obtain a J signal representing the magnetic polarization J of the sample. An analog-to-digital converter is used to convert the H signal and the J signal from analog signals into digital signals; and The data processing unit is used to perform signal processing on the H signal and the J signal, which have been converted into digital signals, to obtain the JH relationship curve of the sample. Under the control of the pulse commutation module, the excitation coil first generates a preset pulse magnetic field to magnetize the sample in a predetermined direction; then, it generates a first reverse pulse magnetic field opposite to the preset pulse magnetic field to measure the first reverse JH relationship curve of the sample; then, it generates a second unidirectional pulse magnetic field in the same direction as the first reverse pulse magnetic field to measure the second unidirectional JH relationship curve of the sample. The data processing unit subtracts the magnetic polarization J values ​​corresponding to the same magnetic field strength H values ​​from the first reverse JH relationship curve and the second same JH relationship curve to obtain the relationship curve between the difference in magnetic polarization J values ​​and the corresponding magnetic field strength H values, which serves as the first half-axis hysteresis loop of the sample.

2. The pulse magnetic measurement device as described in claim 1, wherein, The data processing unit further determines a symmetrical second half-axis hysteresis loop based on the first half-axis hysteresis loop, thereby obtaining the complete hysteresis loop of the sample. The first half-axis hysteresis loop and the second half-axis hysteresis loop correspond to one of the positive half-axis and the other of the negative half-axis of the magnetic field strength H value, respectively.

3. The pulse magnetic measurement device as described in claim 1, wherein, Under the control of the pulse commutation module, the excitation coil also generates a third reverse pulse magnetic field, which is opposite in direction to the second in-phase pulse magnetic field, to measure the third reverse JH relationship curve of the sample; then, it generates a fourth in-phase pulse magnetic field, which is in the same direction as the third reverse pulse magnetic field, to measure the fourth in-phase JH relationship curve of the sample. The data processing unit also subtracts the magnetic polarization J values ​​corresponding to the same magnetic field strength H value from the third reverse JH relationship curve and the fourth same-direction JH relationship curve to obtain the relationship curve between the difference in magnetic polarization J value and the corresponding magnetic field strength H value, which serves as the second half-axis hysteresis loop of the sample, thereby obtaining the complete hysteresis loop of the sample. The first half-axis hysteresis loop and the second half-axis hysteresis loop correspond to one and the other of the positive and negative half-axis of the magnetic field strength H value, respectively.

4. The pulse magnetic measurement device as described in claim 3, wherein, The first reverse pulse magnetic field and the second co-directional pulse magnetic field have the same pulse width, amplitude, and shape. The third reverse pulse magnetic field and the fourth co-directional pulse magnetic field have the same pulse width, amplitude, and shape, and The third reverse pulse magnetic field and the fourth co-directional pulse magnetic field have pulse widths different from those of the first reverse pulse magnetic field and the second co-directional pulse magnetic field.

5. The pulse magnetic measurement device according to any one of claims 1-4, wherein, The sample is cylindrical and has an aspect ratio in the range of 1.125 ± 5%.

6. A pulse magnetism measurement method based on the pulse magnetism measuring device according to any one of claims 1-5, comprising: A preset pulsed magnetic field is generated to magnetize the sample in a predetermined direction; A first reverse pulse magnetic field is generated that is opposite to the direction of the preset pulse magnetic field, and the magnetic field strength H of the first reverse pulse magnetic field and the magnetic polarization J of the sample in the first reverse pulse magnetic field are measured to obtain a first reverse JH relationship curve. A second unidirectional pulsed magnetic field with the same direction as the first reverse pulsed magnetic field is generated, and the magnetic field strength H of the second unidirectional pulsed magnetic field and the magnetic polarization J of the sample in the second unidirectional pulsed magnetic field are measured to obtain a second unidirectional JH relationship curve. Subtract the magnetic polarization J values ​​corresponding to the same magnetic field strength H values ​​from the first reverse JH relationship curve and the second same-direction JH relationship curve to obtain the relationship curve between the difference in magnetic polarization J values ​​and the corresponding magnetic field strength H values, which serves as the first half-axis hysteresis loop of the sample.

7. The pulse magnetism measurement method as described in claim 6, further comprising: Based on the first half-axis hysteresis loop, a symmetrical second half-axis hysteresis loop is determined, thereby obtaining the complete hysteresis loop of the sample. The first half-axis hysteresis loop and the second half-axis hysteresis loop correspond to one of the positive half-axis and the other of the negative half-axis of the magnetic field strength H value, respectively.

8. The pulse magnetism measurement method as described in claim 6, further comprising: A third reverse pulse magnetic field is generated that is opposite to the direction of the second in-direction pulse magnetic field, and the magnetic field strength H of the third reverse pulse magnetic field and the magnetic polarization J of the sample in the third reverse pulse magnetic field are measured to obtain the third reverse JH relationship curve. A fourth unidirectional pulsed magnetic field with the same direction as the third reverse pulsed magnetic field is generated, and the magnetic field strength H of the fourth unidirectional pulsed magnetic field and the magnetic polarization J of the sample in the fourth unidirectional pulsed magnetic field are measured to obtain the fourth unidirectional JH relationship curve. Subtract the magnetic polarization J values ​​corresponding to the same magnetic field strength H values ​​from the third reverse JH relationship curve and the fourth same-direction JH relationship curve to obtain the relationship curve between the difference in magnetic polarization J values ​​and the corresponding magnetic field strength H values. This curve serves as the second half-axis hysteresis loop of the sample, thereby obtaining the complete hysteresis loop of the sample. The first half-axis hysteresis loop and the second half-axis hysteresis loop correspond to one of the positive half-axis and the other of the negative half-axis of the magnetic field strength H values, respectively.

9. The pulse magnetism measurement method as described in claim 8, wherein, The first reverse pulse magnetic field and the second co-directional pulse magnetic field have the same pulse width, amplitude, and shape. The third reverse pulse magnetic field and the fourth co-directional pulse magnetic field have the same pulse width, amplitude, and shape, and The third reverse pulse magnetic field and the fourth co-directional pulse magnetic field have pulse widths different from those of the first reverse pulse magnetic field and the second co-directional pulse magnetic field.

10. The pulse magnetism measurement method according to any one of claims 6-9, wherein, The sample is cylindrical and has an aspect ratio in the range of 1.125 ± 5%.

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