A method and system for testing the magnetoelectric coefficient of a composite magnetoelectric material

Abstract

The present application relates to the technical field of measuring magnetic variables, and specifically relates to a method and system for testing the magnetoelectric coefficient of a composite magnetoelectric material. The method includes: determining the rate of change of the slope of the hysteresis loop based on the degree of inclination of the hysteresis loop between a preset magnetic field intensity range; determining the ratio of the magnetic domain rotation energy threshold based on the volume of the composite magnetoelectric material, in combination with the saturation magnetization intensity and the magnetization intensity at a preset first magnetic field intensity; determining the energy loss coefficient of the composite magnetoelectric material based on the difference in magnetization intensity between a preset second magnetic field intensity and the preset first magnetic field intensity, and combining the rate of change of the slope of the hysteresis loop and the magnetic domain rotation energy threshold to determine the hysteresis compensation factor of the composite magnetoelectric material, and testing the magnetoelectric coefficient of the composite magnetoelectric material. The purpose of the present application is to exclude the influence of the hysteresis effect on the measurement accuracy of the magnetoelectric coefficient and improve the measurement accuracy of the magnetoelectric coefficient of the composite magnetoelectric material.

Description

Technical Field

[0001] This application relates to the technical field of measuring magnetic variables, and specifically relates to a method and system for testing the magnetoelectric coefficient of composite magnetoelectric materials. Background Art

[0002] Magnetoelectric materials refer to a class of materials that can generate polarization under the action of an external magnetic field or magnetization under the action of an external electric field. Their characteristic is the ability to achieve the mutual conversion between magnetic energy and electrical energy, with unique physical properties and potential application values. Composite magnetoelectric materials are materials formed by combining single-phase ferroelectric materials and ferromagnetic materials through a certain method. They combine the characteristics of the ferroelectric phase and the ferromagnetic phase, and generate an indirect magnetoelectric coupling effect through the interfacial interaction between the two phases. Compared with single-phase magnetoelectric materials, they usually have a higher magnetoelectric coupling coefficient and can be used to prepare high-performance magnetoelectric devices.

[0003] The magnetoelectric coefficient is an important physical quantity to measure the performance of magnetoelectric materials, used to describe the ratio between the electric field strength and the magnetic field strength in magnetoelectric materials. The traditional static measurement method measures the change of polarization intensity or magnetization intensity of the material with the magnetic field or electric field under a DC magnetic field and electric field, and then obtains the magnetoelectric coefficient. However, due to the influence of the hysteresis effect, the characteristics of the hysteresis loop of the composite magnetoelectric material are affected, resulting in errors in the measurement of the magnetoelectric coefficient. Summary of the Invention

[0004] In order to solve the above technical problems, the purpose of this application is to provide a method and system for testing the magnetoelectric coefficient of composite magnetoelectric materials, and the specific technical solutions adopted are as follows:

[0005] In a first aspect, an embodiment of this application provides a method for testing the magnetoelectric coefficient of composite magnetoelectric materials, and the method includes the following steps:

[0006] Obtain the hysteresis loop of the composite magnetoelectric material between the preset negative maximum magnetic field strength and the preset positive maximum magnetic field strength, as well as the volume of the composite magnetoelectric material, where the abscissa and ordinate of the hysteresis loop are the magnetic field strength and the magnetization intensity respectively;

[0007] Record the hysteresis loop from increasing the preset negative maximum magnetic field strength to the preset positive maximum magnetic field strength and the hysteresis loop from decreasing the preset positive maximum magnetic field strength to the preset negative maximum magnetic field strength as the rising hysteresis loop and the falling hysteresis loop respectively, and determine the change rate of the slope of the hysteresis loop of the composite magnetoelectric material based on the difference in the inclination degree between the rising hysteresis loop and the falling hysteresis loop within the preset magnetic field strength range;

[0008] Based on the volume of the composite magnetoelectric material, and in combination with the saturation magnetization intensity and the magnetization intensity at the preset first magnetic field strength on the rising hysteresis loop, determine the threshold ratio of the magnetic domain rotation energy of the composite magnetoelectric material;

[0009] Determine the energy loss coefficient of the composite magnetoelectric material based on the difference in magnetization intensity between the preset second magnetic field intensity and the preset first magnetic field intensity on the ascending hysteresis loop;

[0010] Determine the hysteresis compensation factor of the composite magnetoelectric material based on the rate of change of the hysteresis loop slope, the magnetic domain rotation energy threshold ratio, and the energy loss coefficient, and combine the magnetization intensity at each magnetic field intensity to determine the compensated magnetization intensity at each magnetic field intensity on the ascending hysteresis loop;

[0011] Test the magnetoelectric coefficient of the composite magnetoelectric material based on the difference between the magnetic field intensity at the upper limit of the preset magnetic field intensity range on the ascending hysteresis loop and the preset first magnetic field intensity, and the difference in compensated magnetization intensity between the magnetic field intensity at the upper limit of the preset magnetic field intensity range and the preset first magnetic field intensity.

[0012] Preferably, the method for determining the rate of change of the hysteresis loop slope of the composite magnetoelectric material is:

[0013] Calculate the slope of the ascending hysteresis loop and the slope of the descending hysteresis loop within the preset magnetic field intensity range, and denote them as the first slope and the second slope respectively;

[0014] Determine the rate of change of the hysteresis loop slope of the composite magnetoelectric material based on the first slope and the second slope.

[0015] Preferably, determining the rate of change of the hysteresis loop slope of the composite magnetoelectric material based on the first slope and the second slope further includes:

[0016] Calculate the difference and the sum between the first slope and the second slope respectively, and use the ratio of the difference to the sum as the rate of change of the hysteresis loop slope of the composite magnetoelectric material.

[0017] Preferably, the method for determining the magnetic domain rotation energy threshold ratio of the composite magnetoelectric material is:

[0018] The magnetic energy at the preset first magnetic field intensity on the ascending hysteresis loop is expressed as: ; where represents the vacuum permeability; represents the magnetization intensity at the preset first magnetic field intensity on the ascending hysteresis loop; represents the volume of the composite magnetoelectric material;

[0019] The theoretical magnetic energy is expressed as: ; where represents the saturation magnetization intensity;

[0020] The magnetic domain rotation energy threshold ratio of the composite magnetoelectric material is the ratio of the magnetic energy at a preset first magnetic field strength on the ascending hysteresis loop to the theoretical magnetic energy.

[0021] Preferably, the method for determining the energy loss coefficient of the composite magnetoelectric material is as follows:

[0022] The magnetic energy at a preset second magnetic field strength on the ascending hysteresis loop is expressed as: ; where represents the magnetization intensity at the preset second magnetic field strength on the ascending hysteresis loop;

[0023] Obtain the area of the phase interface between the ferromagnetic phase and the ferroelectric phase in the composite magnetoelectric material, as well as the lattice constants of the ferromagnetic phase and the ferroelectric phase, and use Raman spectroscopy to identify the frequency of lattice vibration at the phase interface;

[0024] The energy loss coefficient of the composite magnetoelectric material is expressed as: ; where k represents a preset coefficient; represents the difference in lattice constants between the ferromagnetic phase and the ferroelectric phase in the composite magnetoelectric material; represents the phase interface area of the composite magnetoelectric material; ω represents the frequency of lattice vibration at the phase interface of the composite magnetoelectric material.

[0025] Preferably, the expression of the hysteresis compensation factor of the composite magnetoelectric material is: ; where represents the hysteresis compensation factor of the composite magnetoelectric material; R, P, and C respectively represent the change rate of the slope of the hysteresis loop, the magnetic domain rotation energy threshold ratio, and the energy loss coefficient of the composite magnetoelectric material; norm( ) represents the normalization function.

[0026] Preferably, the expression of the compensated magnetization intensity at each magnetic field strength on the ascending hysteresis loop is: ; where represents the compensated magnetization intensity at the magnetic field strength i on the ascending hysteresis loop; represents the hysteresis compensation factor of the composite magnetoelectric material; represents the magnetization intensity at the magnetic field strength i on the ascending hysteresis loop.

[0027] Preferably, the testing of the magnetoelectric coefficient of the composite magnetoelectric material includes:

[0028] Calculate the difference between the preset first magnetic field strength and the upper limit of the preset magnetic field strength range on the ascending hysteresis loop, denoted as the first difference; calculate the difference in the compensated magnetization intensity between the preset first magnetic field strength and the upper limit of the preset magnetic field strength range on the ascending hysteresis loop, denoted as the second difference;

[0029] Determine the magnetoelectric coefficient of the composite magnetoelectric material based on the first difference and the second difference.

[0030] Preferably, the determining the magnetoelectric coefficient of the composite magnetoelectric material based on the first difference and the second difference further includes: the magnetoelectric coefficient of the composite magnetoelectric material is the ratio of the second difference to the first difference.

[0031] In a second aspect, an embodiment of the present application further provides a system for testing the magnetoelectric coefficient of a composite magnetoelectric material, including a memory, a processor, and a computer program stored in the memory and running on the processor. When the processor executes the computer program, it implements the method for testing the magnetoelectric coefficient of a composite magnetoelectric material described above.

[0032] The present application has at least the following beneficial effects:

[0033] By analyzing the symmetry of the hysteresis loop, the present application constructs the rate of change of the hysteresis loop slope, which reflects the asymmetry of the magnetic domain movement, judges the internal obstacles faced by the magnetic domains when starting to respond to the magnetic field change, and helps to judge the early manifestation of the hysteresis effect; further, by analyzing the difference in magnetic energy between the preset first magnetic field intensity and the preset second magnetic field intensity, the present application constructs the threshold ratio of magnetic domain rotation energy, which reflects the energy barrier required for the magnetic domains to start large-scale stable rotation, and helps to understand the subsequent degree of the hysteresis effect of the composite magnetoelectric material; further, by analyzing the difference in magnetic energy between the preset second magnetic field intensity and the preset first magnetic field intensity, the present application constructs the energy loss coefficient, which reflects the energy conversion and loss when the magnetic domains cross the phase interface, and judges the influence and role of the phase interface in the hysteresis process; by comprehensively considering the rate of change of the hysteresis loop slope, the threshold ratio of magnetic domain rotation energy and the energy loss coefficient, the present application reduces the influence of the hysteresis effect on the measurement accuracy of the magnetoelectric coefficient and improves the measurement accuracy of the magnetoelectric coefficient of the composite magnetoelectric material. Description of the Drawings

[0034] In order to more clearly illustrate the technical solutions and advantages in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0035] Figure 1 It is a flowchart of the steps of a method for testing the magnetoelectric coefficient of a composite magnetoelectric material provided by an embodiment of the present application;

[0036] Figure 2 It is a schematic diagram of a data acquisition module provided by an embodiment of the present application. Figure 2It includes: 1. A composite magnetoelectric material sample, 2. An electromagnet, 3. A magnetic field modulation coil, 4. A digital lock-in amplifier, 5. A gaussmeter, 6. A signal generator, 7. A power amplifier, 8. A numerically controlled magnet power supply, 9. A computer;

[0037] Figure 3 Schematic diagram of the process for obtaining the compensated magnetization intensity provided by an embodiment of the present application. Detailed implementation manners

[0038] In order to further elaborate on the technical means and effects adopted by the present application to achieve the predetermined invention purpose, the following, in conjunction with the accompanying drawings and preferred embodiments, details the specific implementation manners, structures, features, and effects of a method and system for testing the magnetoelectric coefficient of a composite magnetoelectric material proposed according to the present application. In the following description, different "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. In addition, the specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.

[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present application belongs.

[0040] The following specifically describes the specific solutions of a method and system for testing the magnetoelectric coefficient of a composite magnetoelectric material provided by the present application with reference to the accompanying drawings.

[0041] Please refer to Figure 1 , which shows a flowchart of the steps of a method for testing the magnetoelectric coefficient of a composite magnetoelectric material provided by an embodiment of the present application. The method includes the following steps:

[0042] Step S1: Obtain the hysteresis loop of the composite magnetoelectric material between the preset negative maximum magnetic field intensity and the preset positive maximum magnetic field intensity, as well as the volume of the composite magnetoelectric material, where the abscissa and ordinate of the hysteresis loop are the magnetic field intensity and the magnetization intensity, respectively.

[0043] Place the sample made of the composite magnetoelectric material in the magnetic field modulation coil, connect the two electrodes to the input end of the digital lock-in amplifier. The sine wave signal generated by the signal amplifier is supplied to the digital lock-in amplifier as a reference signal, and is also amplified by the power amplifier and then drives the magnetic field modulation coil to generate a differential magnetic field. After the sample undergoes magnetoelectric coupling, a voltage can be detected at the electrodes of the ferroelectric material.

[0044] Preferably, the schematic diagram of the data acquisition module provided in this embodiment is as shown in Figure 2 ; Figure 2 It includes: a composite magnetoelectric material sample 1, an electromagnet 2, a magnetic field modulation coil 3, a digital lock-in amplifier 4, a gaussmeter 5, a signal generator 6, a power amplifier 7, a numerically controlled magnet power supply 8, and a computer 9.

[0045] Under quasi-static conditions, starting from a preset negative maximum magnetic field strength , the magnetic field strength is gradually increased in fixed steps, and the magnetization corresponding to each magnetic field strength value is recorded , until the preset positive maximum magnetic field strength value is reached. Then, starting from , the magnetic field strength is gradually decreased in the same steps back to , and the magnetization corresponding to each magnetic field strength value is also recorded. Based on the magnetization, magnetic field strength, and the point-plotting method, the hysteresis loop of the composite magnetoelectric material is obtained. Among them, the abscissa and ordinate of the hysteresis loop represent the magnetic field strength and magnetization, respectively.

[0046] It should be noted that , , as well as the value of the step size, are all set manually. In this embodiment, the value of is the value of is , and the value of the step size is

[0047] . Implementers can also set them according to specific situations, and this embodiment does not make special restrictions.

[0048] Among them, the process of drawing the hysteresis loop based on the induction intensity and magnetic field strength is a well-known technology, and its specific drawing steps will not be elaborated here.

[0049] In the composite magnetoelectric material, the ferromagnetic phase is generally a magnetostrictive material. The magnetostrictive material has a magnetostrictive effect, which means that when the magnetostrictive material is magnetized in an external magnetic field, the volume and length of the magnetostrictive material will change, and when the external magnetic field disappears, the material will return to its original state.

[0050] Inside magnetic materials, there are many small regions called magnetic domains. The atomic magnetic moments within each magnetic domain are arranged regularly, giving the magnetic domain a certain magnetic direction. In the unmagnetized state, the directions of the magnetic domains in the magnetic material are disordered, and the overall material does not exhibit magnetism externally. When an external magnetic field is applied, processes such as the rotation of magnetic domains and the movement of domain walls occur, causing the directions of the individual magnetic domains to gradually align with the direction of the external magnetic field, and the magnetic material is magnetized. There are a large number of such magnetic domains in ferromagnetic materials, and this magnetic domain structure is the key to the hysteresis phenomenon.

[0051] Since the directions of the magnetic domains inside the magnetic material are disordered in the initial stage, the movement of the magnetic domains is asymmetric. Therefore, this asymmetry can be reflected by the rate of change of the slope of the hysteresis loop. This asymmetry is an early manifestation of the hysteresis effect, which reflects the internal obstacles faced by the magnetic domains when they start to move at low magnetic field intensities, and can preliminarily determine whether there is an obvious hysteresis tendency in the composite magnetoelectric material. Therefore, based on the degree of inclination of the hysteresis loop between the preset magnetic field intensity ranges, the rate of change of the slope of the hysteresis loop of the composite magnetoelectric material is determined to judge whether there is an obvious hysteresis phenomenon in the composite magnetoelectric material. Specifically:

[0052] Although the overall hysteresis loop is non-linear, for the hysteresis loop, near a certain specific magnetic field intensity point, the change in the movement state of the magnetic domains is relatively small, and the relationship between the corresponding magnetization intensity and the magnetic field intensity can be approximated as a linear relationship. Therefore, a linear approximation method can be used to calculate the slope of the local hysteresis loop. Specifically:

[0053] Since the hysteresis loop is a closed curve, the hysteresis loop between the preset magnetic field intensity ranges contains two curves. One curve shows an upward trend where the magnetization intensity increases as the magnetic field intensity increases, and the other curve shows a downward trend where the magnetization intensity decreases as the magnetic field intensity decreases. The hysteresis loop from the preset negative maximum magnetic field intensity increasing to the preset positive maximum magnetic field intensity, and the hysteresis loop from the preset positive maximum magnetic field intensity decreasing to the preset negative maximum magnetic field intensity are respectively denoted as the rising hysteresis loop and the falling hysteresis loop;

[0054] Furthermore, the slopes of the rising hysteresis loop and the falling hysteresis loop within the preset magnetic field intensity range are calculated respectively using linear approximation, and are denoted as the first slope and the second slope respectively;

[0055] Furthermore, the difference and the sum between the first slope and the second slope are calculated respectively, and the ratio of the difference to the sum is used as the rate of change of the slope of the hysteresis loop of the composite magnetoelectric material.

[0056] It should be understood that there are many methods to measure the difference between data. In this embodiment, the absolute value of the difference between the first slope and the second slope is calculated as the difference in the inclination degrees of the ascending hysteresis loop and the descending hysteresis loop. Implementers can also use other methods to measure the difference between data, such as ratios. Regarding the selection of methods for measuring the difference between data, this embodiment does not impose special restrictions.

[0057] It should be noted that the preset magnetic field strength range is set artificially. According to the analysis of this embodiment, since the directions of magnetic domains inside the magnetic material are disordered in the initial stage, the movement of magnetic domains is asymmetric. Therefore, by analyzing the inclination degree of the hysteresis loop within a local range, the significance degree of the hysteresis phenomenon is measured. So, in this embodiment, a relatively small magnetic field strength range is selected as the analysis interval. The value of the preset magnetic field strength range in this embodiment is from -100 Oe to 10 Oe. Under the condition of ensuring that the preset magnetic field strength range is a relatively small range including 0 Oe, implementers can also set it according to specific situations, such as -80 Oe to 20 Oe or -100 Oe to 15 Oe, etc.

[0058] Among them, linear approximation refers to the method of approximating a general function using a linear function. Linear approximation is a well-known technology, and the specific process of representing a complex non-linear function with a simple linear function will not be elaborated here.

[0059] Furthermore, according to the change rate of the slope of the hysteresis loop of the composite magnetoelectric material, it can be understood that in the ascending section where the magnetic field strength increases, the magnetic domains are gradually magnetized by the magnetic field, and their arrangement directions gradually turn to be consistent with the external magnetic field direction. This is a process of magnetic domains changing from a disordered or initial state to an ordered arrangement. However, when the magnetic field strength decreases, the magnetic domains do not immediately return to the original state. Instead, due to the interaction between magnetic domains, the resistance to the movement of magnetic domains inside the material, and the influence of the phase interface factor, there is a lag in the reversal process of magnetic domains, which further causes the magnetization intensity to show different change trends in the ascending and descending sections. The greater the difference between the first slope and the second slope, the greater the change rate of the slope of the hysteresis loop, indicating that the magnetic domains face greater internal resistance when starting to respond to the change of the magnetic field. For example, there is a strong magnetostatic energy or magnetocrystalline anisotropy between magnetic domains, or there are more impurities or defects in the material that interfere with the movement of magnetic domains. In this case, the hysteresis phenomenon is more obvious in the initial stage, and the magnetic domains need more energy to overcome these obstacles to achieve the same change in magnetization intensity. On the contrary, the smaller the difference between the first slope and the second slope, the smaller the change rate of the slope of the hysteresis loop, indicating that at low magnetic field strengths, the movement of magnetic domains is relatively symmetric, that is, the changes in magnetization intensity are relatively similar during the increase and decrease of the magnetic field strength.

[0060] Step S3: Determine the magnetic domain rotation energy threshold ratio of the composite magnetoelectric material based on the volume of the composite magnetoelectric material, in combination with the saturation magnetization intensity and the magnetization intensity at a preset first magnetic field intensity on the ascending hysteresis loop.

[0061] From the perspective of the physical mechanism of magnetic domain rotation, the magnetic domains need to overcome a certain energy barrier to start large-scale and stable rotation. When the magnetic field intensity is low, the rotation of the magnetic domains is restricted by factors such as the internal anisotropy energy and the interaction between magnetic domains. Only when the energy provided by the magnetic field intensity is sufficient to overcome these restrictions will the magnetic domains start large-scale rotation. Therefore, during the process of gradually increasing the magnetic field intensity, the slope of the hysteresis loop will change. When the slope begins to show an obvious and relatively stable increasing or decreasing trend, this usually means that the magnetic domains start large-scale and regular rotation. Therefore, the magnetic field intensity at the inflection point of the hysteresis loop during the increase of the magnetic field intensity is taken as the value of the preset first magnetic field intensity.

[0062] It should be noted that only the ascending hysteresis loop is considered in all the following content of this embodiment. This is because during the stage corresponding to the descending hysteresis loop of the composite magnetoelectric material, the composite magnetoelectric material will experience magnetic hysteresis loss, which is due to the loss of internal energy when the magnetic domains reorient. Therefore, in order to more accurately measure the magnetoelectric coefficient of the composite magnetoelectric material, the analysis object of the following content is only the ascending hysteresis loop. Specifically:

[0063] The ratio of the magnetic energy at the turning point to the theoretical magnetic energy can reflect the influence of the energy barrier on the magnetic domain movement, and further reflect the hysteresis degree of the hysteresis effect. Therefore, based on the volume of the composite magnetoelectric material, in combination with the saturation magnetization intensity and the magnetization intensity at the preset first magnetic field intensity, determine the magnetic domain rotation energy threshold ratio of the composite magnetoelectric material. Specifically:

[0064] The magnetic energy at the preset first magnetic field intensity on the ascending hysteresis loop The expression is: ; In the formula, represents the vacuum permeability, and its value is ; represents the magnetization intensity at the preset first magnetic field intensity on the ascending hysteresis loop; represents the volume of the composite magnetoelectric material;

[0065] The theoretical magnetic energy The expression is: ; In the formula, represents the saturation magnetization intensity;

[0066] The magnetic domain rotation energy threshold ratio of the composite magnetoelectric material The expression is: ;

[0067] It should be noted that the saturation magnetization intensity is a well-known parameter in the hysteresis loop. The saturation magnetization intensity refers to the maximum magnetization intensity that a magnetic material can reach when magnetized in an external magnetic field. It can be obtained from material manuals and experimental tests. In this embodiment, the value of the saturation magnetization intensity is , and the magnetization intensity at the preset first magnetic field intensity on the rising hysteresis loop is .

[0068] Among them, the vacuum permeability is a well-known parameter, and its value is .

[0069] It can be understood from the energy loss coefficient of the composite magnetoelectric material that the greater the magnetic energy at the preset first magnetic field intensity is and the closer it is to the theoretical magnetic energy, the greater the magnetic domain rotation energy threshold ratio is, indicating that a higher energy is required for the magnetic domains to start large-scale rotation, that is, the magnetic domains are restricted by a larger internal energy barrier. This may be because the magnetic domain structure inside the material is tight, the interaction between magnetic domains is strong, or the magnetic phase of the material has a high anisotropy. Therefore, the hysteresis effect is more obvious in the stage when the magnetic domains start to rotate, because the magnetic field intensity needs to reach a higher value to enable the magnetic domains to overcome the energy threshold and start large-scale rotation. Moreover, during the rotation process, the magnetic domains will also show strong hysteresis due to this higher energy restriction. On the contrary, the greater the difference between the magnetic energy at the preset first magnetic field intensity and the theoretical magnetic energy is, and the smaller the magnetic domain rotation energy threshold ratio is, the smaller the hysteresis effect is in the stage when the magnetic domains start to rotate, and the magnetic domains can respond to the change of the magnetic field intensity more timely.

[0070] Step S4: Determine the energy loss coefficient of the composite magnetoelectric material based on the difference in magnetization intensity between the preset second magnetic field intensity and the preset first magnetic field intensity on the rising hysteresis loop.

[0071] Considering only the rotation of magnetic domains is not enough to reflect the hysteresis effect. The influence of the phase interface also needs to be considered. In the composite magnetoelectric material, the phase interface is an important region during the movement of magnetic domains. Due to the difference in lattice constants between different phases, energy conversion and loss will occur when magnetic domains cross the phase interface.

[0072] The lattice mismatch at the phase interface will cause the magnetic domains to distort when crossing the interface, thereby consuming energy. By studying the energy loss at the phase interface, the influence of the complex microstructure of the composite magnetoelectric material on the hysteresis effect can be deeply understood. Different phase compositions, phase distributions, and the properties of the phase interface will all affect the behavior of magnetic domains at the interface, and thus affect the hysteresis characteristics of the entire material.

[0073] The value of the preset second magnetic field strength is generally less than the magnetic field strength that causes the material to reach saturation magnetization, but should be high enough to cover the process of magnetic domains starting to rotate massively to approaching saturation magnetization. When the magnetization reaches saturation magnetization, at this time, almost all magnetic domains are aligned in the magnetic field direction. Therefore, in this embodiment, the value of the preset second magnetic field strength is the magnetic field strength corresponding to 0.8 times the saturation magnetization strength.

[0074] Further, based on the difference in magnetization intensity between the preset second magnetic field strength and the preset first magnetic field strength on the ascending hysteresis loop, the energy loss coefficient of the composite magnetoelectric material is determined, specifically:

[0075] The magnetic energy at the preset second magnetic field strength on the ascending hysteresis loop The expression is: ; In the formula, represents the magnetization intensity at the preset second magnetic field strength on the ascending hysteresis loop;

[0076] Further, obtain the area of the phase interface between the ferromagnetic phase and the ferroelectric phase in the composite magnetoelectric material, as well as the lattice constants of the ferromagnetic phase and the ferroelectric phase, and use Raman spectroscopy to identify the frequency of lattice vibration at the phase interface;

[0077] Further, based on the area of the phase interface between the ferromagnetic phase and the ferroelectric phase in the composite magnetoelectric material, the lattice constants of the ferromagnetic phase and the ferroelectric phase, and the frequency of lattice vibration at the phase interface, the energy loss coefficient of the composite magnetoelectric material is determined, specifically:

[0078] The expression for the energy loss coefficient C of the composite magnetoelectric material is: ; k represents a preset coefficient; represents the difference in lattice constants between the ferromagnetic phase and the ferroelectric phase in the composite magnetoelectric material; represents the phase interface area of the composite magnetoelectric material; ω represents the frequency of lattice vibration at the phase interface of the composite magnetoelectric material.

[0079] It should be noted that there are many methods to measure the difference between data. In this embodiment, the difference in lattice constants between the ferromagnetic phase and the ferroelectric phase in the composite magnetoelectric material is measured by calculating the absolute value of the difference in lattice constants, and implementers can also use other methods to measure the difference between data such as ratios. There are no special restrictions on the selection of methods for measuring the difference between data in this embodiment.

[0080] It should be understood that represents a preset coefficient, which can be obtained by data fitting by measuring materials with different lattice mismatch degrees, and the value range is usually between and in this embodiment, the value is , and implementers can also set it according to specific situations, and there are no special restrictions in this embodiment.

[0081] Among them, the process of using Raman spectroscopy to identify the frequency of lattice vibration at the phase interface is a well-known technology, and its specific steps will not be elaborated here.

[0082] According to the energy loss coefficient of the composite magnetoelectric material, it can be understood that the larger the energy loss coefficient, the larger the proportion of energy loss at the phase interface in the total magnetic energy change, indicating that the phase interface plays a key role in the hysteresis process. This may be due to a large lattice mismatch at the phase interface, so the greater the difference between the lattice constants, or the structure of the phase interface causes large distortions and energy dissipation when magnetic domains cross. On the contrary, the smaller the energy loss coefficient, the smoother the movement of magnetic domains at the phase interface during the change of magnetic field strength, the better the lattice matching at the phase interface, that is, the smaller the difference between the lattice constants, and the smaller the hindrance of the interaction at the phase interface to the movement of magnetic domains, that is, the smaller the hysteresis effect.

[0083] Step S5: Based on the rate of change of the slope of the hysteresis loop, the ratio of the magnetic domain rotation energy threshold, and the energy loss coefficient, determine the hysteresis compensation factor of the composite magnetoelectric material, and combine the magnetization intensity at each magnetic field strength to determine the compensated magnetization intensity at each magnetic field strength on the ascending hysteresis loop; Based on the difference between the magnetic field strength at the upper limit of the preset magnetic field strength range and the preset first magnetic field strength on the ascending hysteresis loop, and the difference in the compensated magnetization intensity between the magnetic field strength at the upper limit of the preset magnetic field strength range and the preset first magnetic field strength, test the magnetoelectric coefficient of the composite magnetoelectric material.

[0084] Based on the rate of change of the slope of the hysteresis loop, the ratio of the magnetic domain rotation energy threshold, and the energy loss coefficient, determine the hysteresis compensation factor of the composite magnetoelectric material, and combine the magnetization intensity at each magnetic field strength to determine the compensated magnetization intensity at each magnetic field strength on the ascending hysteresis loop, specifically as follows:

[0085] The hysteresis compensation factor of the composite magnetoelectric material has the following expression: ; where R, P, and C respectively represent the rate of change of the slope of the hysteresis loop, the ratio of the magnetic domain rotation energy threshold, and the energy loss coefficient of the composite magnetoelectric material; norm( ) represents the normalization function.

[0086] According to the hysteresis compensation factor of the composite magnetoelectric material, it can be understood that if the rate of change of the slope of the hysteresis loop is larger, the ratio of the magnetic domain rotation energy threshold is larger, and the energy loss coefficient is larger, then the hysteresis compensation factor is larger, indicating that the hysteresis effect is more serious and the impact on the calculation of the magnetoelectric coefficient of the composite magnetoelectric material is greater. Therefore, it is more necessary to compensate the magnetoelectric coefficient of this composite material; on the contrary, if the rate of change of the slope of the hysteresis loop is smaller, the ratio of the magnetic domain rotation energy threshold is smaller, and the energy loss coefficient is smaller, it indicates that the hysteresis effect of the composite magnetoelectric material is smaller, so the compensation is also smaller.

[0087] Further, the calculation of the magnetoelectric coefficient is compensated by the hysteresis compensation factor to obtain a more accurate magnetoelectric coefficient. Specifically:

[0088] First, each measured magnetization intensity is compensated using the magnetoelectric coefficient. Specifically:

[0089] The expression for the compensated magnetization intensity at each magnetic field strength on the ascending hysteresis loop is: ; where represents the compensated magnetization intensity at the magnetic field strength i on the ascending hysteresis loop; represents the magnetization intensity at the magnetic field strength i on the ascending hysteresis loop.

[0090] Preferably, the schematic diagram of the process for obtaining the compensated magnetization intensity provided in this embodiment is as shown in Figure 3 shown.

[0091] Secondly, the magnetoelectric coefficient is calculated using the compensated magnetization intensity and the corresponding magnetic field strength. Specifically:

[0092] Calculate the difference between the first magnetic field strength on the preset ascending hysteresis loop and the magnetic field strength at the upper limit of the preset magnetic field strength range, denoted as the first difference; calculate the difference between the compensated magnetization intensities between the preset first magnetic field strength and the magnetic field strength at the upper limit of the preset magnetic field strength range on the ascending hysteresis loop, denoted as the second difference;

[0093] The magnetoelectric coefficient of the composite magnetoelectric material is the ratio of the second difference to the first difference.

[0094] So far, in this embodiment, the rate of change of the slope of the hysteresis curve is calculated by considering the influence of the initial magnetic domain rotation on the hysteresis curve; then, the ratio of the magnetic domain rotation energy threshold is calculated by combining the magnetic energy at the turning point where the magnetic domains start to rotate on a large scale; further, considering the influence of the energy loss caused by the magnetic domain rotation at the phase interface on the hysteresis effect, the energy loss coefficient is calculated, and finally the hysteresis compensation factor is obtained. By calculating the hysteresis compensation factor through the influence of the magnetic domain rotation of the internal microstructure of the composite magnetoelectric material on the hysteresis effect, and further calculating the magnetoelectric coefficient by considering the hysteresis compensation factor, the interference of the hysteresis phenomenon on the measurement result can be effectively reduced, making the calculated magnetoelectric coefficient closer to the true magnetoelectric conversion performance of the material and improving the measurement accuracy of the magnetoelectric coefficient of the composite magnetoelectric material.

[0095] It should be noted that the preset magnetic field strength range, the preset first magnetic field strength, and the preset second magnetic field strength in this embodiment are all between the preset negative maximum magnetic field strength and the preset positive maximum magnetic field strength.

[0096] Based on the same inventive concept as the above method, an embodiment of the present application further provides a system for testing the magnetoelectric coefficient of a composite magnetoelectric material, including a memory, a processor, and a computer program stored in the memory and running on the processor. When the processor executes the computer program, it implements any one of the above methods for testing the magnetoelectric coefficient of a composite magnetoelectric material.

[0097] It should be noted that the above sequence of embodiments of the present application is only for description and does not represent the superiority or inferiority of the embodiments. In addition, the above specific embodiments of the present specification have been described. Further, the processes depicted in the accompanying drawings do not necessarily require the particular order or sequential order shown to achieve the desired results. In certain embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0098] Each embodiment in this specification is described in a progressive manner. The same or similar parts among the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments.

[0099] The above are only the preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for testing the magnetoelectric coefficient of a composite magnetoelectric material, characterized in that: The method comprises the following steps: Obtaining a hysteresis loop of the composite magnetoelectric material between a preset negative maximum magnetic field intensity and a preset positive maximum magnetic field intensity, and the volume of the composite magnetoelectric material, wherein the horizontal and vertical coordinates of the hysteresis loop are the magnetic field intensity and the magnetization intensity, respectively; The hysteresis loop between the preset negative maximum magnetic field intensity increasing to the preset positive maximum magnetic field intensity, and the hysteresis loop between the preset positive maximum magnetic field intensity decreasing to the preset negative maximum magnetic field intensity are respectively recorded as an ascending hysteresis loop and a descending hysteresis loop, and the rate of change of the slope of the hysteresis loop of the composite magneto-electric material is determined based on the difference in the inclination between the ascending hysteresis loop and the descending hysteresis loop within the preset magnetic field intensity range; Determine the magnetic domain rotation energy threshold ratio of the composite magnetoelectric material based on the volume of the composite magnetoelectric material and in combination with the saturation magnetization and the magnetization at a preset first magnetic field intensity on the rising hysteresis loop; Determining the energy loss coefficient of the composite magneto-electric material based on the difference in magnetization intensity between the preset second magnetic field intensity and the preset first magnetic field intensity on the rising hysteresis loop; The hysteresis compensation factor of the composite magnetoelectric material is determined based on the slope change rate of the hysteresis loop, the magnetic domain rotation energy threshold ratio and the energy loss coefficient. , the calculation formula is: ; In the formula, R, P, and C represent the slope change rate of the hysteresis loop of the composite magnetoelectric material, the magnetic domain rotation energy threshold ratio, and the energy loss coefficient, respectively; norm () represents the normalization function, and combined with the magnetization intensity at each magnetic field intensity, the compensation magnetization intensity at each magnetic field intensity on the rising hysteresis loop is determined, and the calculation formula is: ; In the formula, It represents the compensation magnetization intensity at the magnetic field intensity i on the rising hysteresis loop; Represents the hysteresis compensation factor of the composite magnetoelectric material; It represents the magnetization intensity at the magnetic field intensity i on the rising hysteresis loop; Based on the difference between the magnetic field strength at the upper limit of the preset magnetic field strength range on the rising hysteresis loop and the preset first magnetic field strength, and the difference in the compensating magnetization intensity between the magnetic field strength at the upper limit of the preset magnetic field strength range and the preset first magnetic field strength, the magnetoelectric coefficient of the composite magnetoelectric material is tested.

2. A method for testing the magnetoelectric coefficient of a composite magnetoelectric material as claimed in claim 1, characterized in that: The method for determining the slope change rate of the hysteresis loop of the composite magnetoelectric material is: The slope of the rising hysteresis loop and the slope of the falling hysteresis loop within the preset magnetic field intensity range are calculated and recorded as the first slope and the second slope respectively; Based on the first slope and the second slope, a rate of change of a slope of a hysteresis loop of the composite magneto-electric material is determined.

3. A method for testing the magnetoelectric coefficient of a composite magnetoelectric material as claimed in claim 2, characterized in that: The step of determining the slope change rate of the hysteresis loop of the composite magneto-electric material based on the first slope and the second slope further comprises: The difference and the sum of the first slope and the second slope are calculated respectively, and the ratio of the difference to the sum is used as the slope change rate of the hysteresis loop of the composite magneto-electric material.

4. A method for testing the magnetoelectric coefficient of a composite magnetoelectric material as claimed in claim 1, characterized in that: The method for determining the magnetic domain rotation energy threshold ratio of the composite magnetoelectric material is as follows: The magnetic energy at the preset first magnetic field strength on the rising hysteresis loop The expression is: ; In the formula, represents the vacuum permeability; Indicates the magnetization intensity at a preset first magnetic field intensity on the rising hysteresis loop; represents the volume of composite magnetoelectric material; Theoretical magnetic energy The expression is: ; In the formula, represents the saturation magnetization; The magnetic domain rotation energy threshold ratio of the composite magnetoelectric material is the ratio of the magnetic energy at a preset first magnetic field intensity on the rising hysteresis loop to the theoretical magnetic energy.

5. A method for testing the magnetoelectric coefficient of a composite magnetoelectric material as claimed in claim 4, characterized in that: The method for determining the energy loss coefficient of the composite magnetoelectric material is: The magnetic energy at the preset second magnetic field strength on the rising hysteresis loop The expression is: ; In the formula, Indicates the magnetization intensity at a preset second magnetic field intensity on the rising hysteresis loop; Obtaining the area of ​​the phase interface between the ferromagnetic phase and the ferroelectric phase in the composite magnetoelectric material and the lattice constants of the ferromagnetic phase and the ferroelectric phase, and using Raman spectroscopy to identify the frequency of lattice vibration at the phase interface; Energy loss coefficient of composite magnetoelectric materials The expression is: ; In the formula, k represents the preset coefficient; It represents the difference in lattice constant between ferromagnetic phase and ferroelectric phase in composite magnetoelectric material; represents the phase interface area of ​​the composite magnetoelectric material; ω represents the frequency of lattice vibration at the phase interface of the composite magnetoelectric material.

6. A method for testing the magnetoelectric coefficient of a composite magnetoelectric material as claimed in claim 1, characterized in that: The magnetoelectric coefficient of the composite magnetoelectric material is tested, including: Calculate the difference between the preset first magnetic field intensity on the rising hysteresis loop and the magnetic field intensity at the upper limit of the preset magnetic field intensity range, recorded as the first difference; calculate the difference between the preset first magnetic field intensity on the rising hysteresis loop and the magnetic field intensity at the upper limit of the preset magnetic field intensity range, recorded as the second difference; Based on the first difference and the second difference, a magnetoelectric coefficient of the composite magnetoelectric material is determined.

7. A method for testing the magnetoelectric coefficient of a composite magnetoelectric material as claimed in claim 6, characterized in that: The method of determining the magnetoelectric coefficient of the composite magnetoelectric material based on the first difference and the second difference further includes: the magnetoelectric coefficient of the composite magnetoelectric material is the ratio of the second difference to the first difference.

8. A system for testing the magnetoelectric coefficient of a composite magnetoelectric material, comprising a memory, a processor, and a computer program stored in the memory and running on the processor, characterized in that: When the processor executes the computer program, the method for testing the magnetoelectric coefficient of a composite magnetoelectric material as described in any one of claims 1 to 7 is implemented.

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