Method and system for testing magnetoelectric coefficient of composite magnetoelectric material

Abstract

The invention relates to the technical field of magnetic variable measurement, in particular to a method and system for testing the magnetoelectric coefficient of a composite magnetoelectric material, and the method comprises the steps: determining the hysteresis loop slope change rate based on the hysteresis loop inclination degree in a preset magnetic field intensity range; determining a magnetic domain rotation energy threshold value ratio 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; and determining a complex energy loss coefficient based on the magnetization intensity difference between the preset second magnetic field intensity and the preset first magnetic field intensity, determining a hysteresis compensation factor of the composite magnetoelectric material in combination with the hysteresis loop slope change rate and the magnetic domain rotation energy threshold, and testing the magnetoelectric coefficient of the composite magnetoelectric material. The invention aims to eliminate the influence of the hysteresis effect on the measurement precision of the magnetoelectric coefficient and improve the measurement precision of the magnetoelectric coefficient of the composite magnetoelectric material.

Description

Technical Field

[0001] The present application relates to the technical field of measuring magnetic variables, and in particular to a method and system for testing the magnetoelectric coefficient of a composite magnetoelectric material. Background Art

[0002] Magnetoelectric materials refer to a class of materials that can generate electric polarization under the action of an external magnetic field, or can generate magnetization under the action of an external electric field. They are characterized by the ability to achieve mutual conversion between magnetic energy and electric energy, and have unique physical properties and potential application value. Composite magnetoelectric materials are materials that are composited by a certain method with single-phase ferroelectric materials and ferromagnetic materials. They combine the characteristics of ferroelectric phase and ferromagnetic phase, and produce indirect magnetoelectric coupling effect through the interface interaction of 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. It is 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 the polarization strength or magnetization strength of the material with the magnetic field or electric field under the 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 will be 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. The technical solutions adopted are as follows: In a first aspect, an embodiment of the present application provides a method for testing the magnetoelectric coefficient of a composite magnetoelectric material, the method comprising 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; Based on the change rate of the slope of the hysteresis loop, the magnetic domain rotation energy threshold ratio and the energy loss coefficient, the hysteresis compensation factor of the composite magnetoelectric material is determined, 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; 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.

[0005] Preferably, the method for determining the rate of change of the slope 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.

[0006] Preferably, 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.

[0007] Preferably, the method for determining the magnetic domain rotation energy threshold ratio of the composite magnetoelectric material is: The magnetic energy at the preset first magnetic field strength on the rising hysteresis loop The expression is: ; In the formula, represents the magnetic permeability of vacuum; 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.

[0008] Preferably, 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.

[0009] Preferably, the expression of the hysteresis compensation factor of the composite magnetoelectric material is: ; In the formula, represents the hysteresis compensation factor of the composite magnetoelectric material; R, P, 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.

[0010] Preferably, the expression of the compensation magnetization intensity at each magnetic field intensity on the rising hysteresis loop 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.

[0011] Preferably, the testing of the magnetoelectric coefficient of the composite magnetoelectric material includes: 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.

[0012] Preferably, 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.

[0013] In the second aspect, an embodiment of the present application also provides 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, wherein the processor implements the above-mentioned method for testing the magnetoelectric coefficient of a composite magnetoelectric material when executing the computer program.

[0014] This application has at least the following beneficial effects: The present application constructs the rate of change of the slope of the hysteresis loop by analyzing the symmetry of the hysteresis loop, which reflects the asymmetry of the movement of the magnetic domains, and determines the internal obstacles faced by the magnetic domains when they begin to respond to changes in the magnetic field, which helps to determine the early manifestations of the hysteresis effect; further, by analyzing the difference in magnetic energy between a preset first magnetic field strength and a preset second magnetic field strength, a threshold ratio of magnetic domain rotation energy is constructed, which reflects the energy barrier required for the magnetic domains to begin large-scale stable rotation, and helps to understand the extent of the hysteresis effect of the composite magnetoelectric material; further, by analyzing the difference in magnetic energy between a preset second magnetic field strength and a preset first magnetic field strength, an energy loss coefficient is constructed, which reflects the energy conversion and loss of the magnetic domains when passing through the phase interface, and determines the influence and role of the phase interface in the hysteresis process; the present application reduces the influence of the hysteresis effect on the measurement accuracy of the magnetoelectric coefficient by comprehensively considering the rate of change of the slope of the hysteresis loop, the threshold ratio of magnetic domain rotation energy and the energy loss coefficient, and improves the measurement accuracy of the magnetoelectric coefficient of the composite magnetoelectric material. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions and advantages in the embodiments of the present application or the prior art, the drawings required for use in the embodiments or the prior art descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0016] Figure 1 A flowchart of a method for testing the magnetoelectric coefficient of a composite magnetoelectric material provided in one embodiment of the present application; Figure 2 A schematic diagram of a data acquisition module provided in one embodiment of the present application, Figure 2 Included: 1. Composite magnetoelectric material sample, 2. Electromagnet, 3. Magnetic field modulation coil, 4. Digital lock-in amplifier, 5. Gauss meter, 6. Signal generator, 7. Power amplifier, 8. Digital control magnet power supply, 9. Computer; Figure 3 A schematic diagram of a process for obtaining compensated magnetization intensity provided in one embodiment of the present application. DETAILED DESCRIPTION

[0017] In order to further explain the technical means and effects adopted by the present application to achieve the predetermined invention purpose, the following is a detailed description of the method and system for testing the magnetoelectric coefficient of a composite magnetoelectric material proposed in the present application, its specific implementation method, structure, characteristics and effects, in combination with the accompanying drawings and preferred embodiments. In the following description, different "one embodiment" or "another embodiment" does not necessarily refer to the same embodiment. In addition, specific features, structures or characteristics in one or more embodiments may be combined in any suitable form.

[0018] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0019] The following is a detailed description of a method and system for testing the magnetoelectric coefficient of a composite magnetoelectric material provided by the present application in conjunction with the accompanying drawings.

[0020] See also Figure 1 , which shows a flowchart of a method for testing the magnetoelectric coefficient of a composite magnetoelectric material provided by an embodiment of the present application, the method comprising the following steps: Step S1: Obtain the hysteresis loop of the composite magnetoelectric material from a preset negative maximum magnetic field intensity to 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.

[0021] A sample made of composite magnetoelectric material is placed in a magnetic field modulation coil, and two electrodes are connected to the input of a digital phase-locked amplifier. The sinusoidal wave signal generated by the signal amplifier is supplied to the digital phase-locked amplifier as a reference signal, and is amplified by a power amplifier to drive the magnetic field modulation coil to generate a differential magnetic field. After the sample undergoes magnetoelectric coupling, voltage can be detected at the ferroelectric material electrodes.

[0022] Preferably, the data acquisition module schematic diagram provided in this embodiment is as follows Figure 2 As shown; Figure 2 The invention comprises: a composite magnetoelectric material sample 1, an electromagnet 2, a magnetic field modulation coil 3, a digital lock-in amplifier 4, a Gauss meter 5, a signal generator 6, a power amplifier 7, a digitally controlled magnet power supply 8, and a computer 9.

[0023] Under quasi-static conditions, the magnetic field strength is from the preset negative to the maximum , gradually increase the magnetic field strength with a fixed step size, and record each magnetic field strength value The corresponding magnetization intensity , until the preset maximum positive magnetic field strength value is reached . Then, from Start by gradually reducing the magnetic field strength with the same step length back to , and also record the magnetization intensity corresponding to each magnetic field intensity value, and obtain the hysteresis loop of the composite magnetoelectric material based on the magnetization intensity and magnetic field intensity and the plotting method. Among them, the horizontal and vertical coordinates of the hysteresis loop represent the magnetic field intensity and the magnetization intensity respectively.

[0024] It should be noted that , The values ​​of and step length are all set manually. In this embodiment, The value of , The value of The step length is The implementer can also set it according to the specific situation, and this embodiment does not impose any special restrictions.

[0025] The process of drawing a hysteresis loop based on the induction intensity and the magnetic field intensity is a well-known technology, and the specific drawing steps are not repeated here.

[0026] Step S2: 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 the rising hysteresis loop and the falling hysteresis loop, and the rate of change of the slope of the hysteresis loop of the composite magnetoelectric material is determined based on the difference in inclination between the rising hysteresis loop and the falling hysteresis loop within the preset magnetic field intensity range.

[0027] In composite magnetoelectric materials, the ferromagnetic phase is generally a magnetostrictive material. Magnetostrictive materials have a magnetostrictive effect. The magnetostrictive effect means that when the magnetostrictive material is magnetized in an external magnetic field, the volume and length of the magnetostrictive material will change. When the external magnetic field disappears, the material returns to its original state.

[0028] There are many small areas inside magnetic materials, which are called magnetic domains. The atomic magnetic moments inside each magnetic domain are arranged regularly, so that the magnetic domain has a certain magnetic direction. In the unmagnetized state, the direction of the magnetic domains in the magnetic material is chaotic, and the whole is not magnetic to the outside. When an external magnetic field is applied, the magnetic domains will rotate and the domain walls will move, so that the direction of each magnetic domain gradually tends to 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.

[0029] Since the direction of the magnetic domains inside the magnetic material is chaotic in the initial stage, the movement of the magnetic domains is asymmetric. Therefore, this asymmetry can be reflected by the slope change rate of the hysteresis loop. This asymmetry is an early manifestation of the hysteresis effect. It reflects the internal obstacles faced by the magnetic domains when they start to move at low magnetic field strengths. It can preliminarily determine whether the composite magnetoelectric material has obvious hysteresis tendency. Therefore, based on the inclination of the hysteresis loop between the preset magnetic field strength range, the slope change rate of the hysteresis loop of the composite magnetoelectric material is determined to determine whether the composite magnetoelectric material has obvious hysteresis phenomenon, specifically: Although the hysteresis loop is nonlinear as a whole, for the hysteresis loop, near a certain magnetic field strength point, the motion state of the magnetic domain changes relatively little, and the corresponding relationship between the magnetization intensity and the magnetic field strength can be approximated as a linear relationship. Therefore, the linear approximation method can be used to calculate the slope of the local hysteresis loop. Specifically: Since the hysteresis loop is a closed curve, the hysteresis loop within the preset magnetic field strength range includes two curves, one of which increases with the increase of the magnetic field strength, and shows an upward trend; the other decreases with the decrease of the magnetic field strength, and shows a downward trend. The hysteresis loop between the preset negative maximum magnetic field strength and the preset positive maximum magnetic field strength, and the hysteresis loop between the preset positive maximum magnetic field strength and the preset negative maximum magnetic field strength are recorded as an upward hysteresis loop and a downward hysteresis loop, respectively. Further, the slope of the rising hysteresis loop and the slope of the falling hysteresis loop within the preset magnetic field intensity range are calculated by linear approximation, and are recorded as the first slope and the second slope respectively; Furthermore, 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 rate of change of the slope of the hysteresis loop of the composite magneto-electric material.

[0030] It should be understood that there are many methods for measuring the difference between data. In this embodiment, the absolute value of the difference between the first slope and the second slope is calculated as a measure of the difference between the inclinations of the rising hysteresis loop and the falling hysteresis loop. The implementer may also use other methods for measuring the difference between data, such as ratios. This embodiment does not impose any special restrictions on the selection of methods for measuring the difference between data.

[0031] It should be noted that the preset magnetic field strength range is artificially set. According to the analysis of this embodiment, since the direction of the magnetic domains inside the magnetic material is chaotic in the initial stage, the movement of the magnetic domains is asymmetric. Therefore, the significance of the hysteresis phenomenon is measured by analyzing the inclination of the hysteresis loop in the local range. Therefore, in this embodiment, a smaller magnetic field strength range is selected as the analysis interval. In this embodiment, the value of the preset magnetic field strength range is -100Oe to 10Oe. While ensuring that the preset magnetic field strength range is a smaller range including 0Oe, the implementer can also set it according to the specific situation, such as -80Oe to 20Oe or -100Oe to 15Oe.

[0032] Among them, linear approximation refers to a method of using a linear function to approximate a general function. Linear approximation is a well-known technology, and the specific process of expressing a complex nonlinear function with a simple linear function will not be repeated here.

[0033] Further, according to the change rate of the slope of the hysteresis loop of the composite magnetoelectric material, it can be understood that in the rising section where the magnetic field intensity increases, the magnetic domain is gradually magnetized by the magnetic field, and its arrangement direction gradually turns to be consistent with the direction of the external magnetic field. This is a process in which the magnetic domain is arranged from a disordered or initial state to an ordered arrangement. However, when the magnetic field intensity decreases, the magnetic domain does not immediately return to its original state, but due to the interaction between the magnetic domains, the resistance to the movement of the magnetic domains inside the material, and the influence of the phase interface factors, the reversal process of the magnetic domain is delayed, which makes the magnetization intensity show different trends in the rising section and the falling section. 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 domain faces greater internal resistance when it begins to respond to changes in the magnetic field, such as strong static magnetic energy or anisotropy between the magnetic domains, or more impurities or defects in the material interfere with the movement of the 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 rate of change of the slope of the hysteresis loop, which means that at low magnetic field strength, the movement of the magnetic domains is relatively symmetrical, that is, the change in magnetization intensity is relatively similar during the increase and decrease of magnetic field strength.

[0034] Step S3: 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.

[0035] From the perspective of the physical mechanism of magnetic domain rotation, the magnetic domains need to overcome certain energy barriers to begin large-scale and stable rotation. When the magnetic field intensity is low, the rotation of the magnetic domains is limited by factors such as internal anisotropy and interaction between magnetic domains. Only when the energy provided by the magnetic field intensity is sufficient to overcome these limitations will the magnetic domains begin to rotate on a large scale. Therefore, as the magnetic field intensity gradually increases, the slope of the hysteresis loop will change. When the slope begins to show an obvious and relatively stable trend of increase or decrease, this usually means that the magnetic domains begin to rotate on a large scale and regularly. Therefore, the magnetic field intensity at the inflection point of the hysteresis loop during the increase in magnetic field intensity is used as the value of the preset first magnetic field intensity.

[0036] It should be noted that in the present embodiment, only the ascending hysteresis loop is considered in all the following contents. This is because the composite magnetoelectric material will experience hysteresis loss in the stage corresponding to the descending hysteresis loop. This is due to the loss of internal energy when the magnetic domains are reoriented. Therefore, in order to more accurately test the magnetoelectric coefficient of the composite magnetoelectric material, the analysis object of the following contents is only for the ascending hysteresis loop, specifically: 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 movement of the magnetic domains, and further reflect the degree of hysteresis of the hysteresis effect. Therefore, based on the volume of the composite magnetoelectric material, and in combination with the saturation magnetization and the magnetization at the preset first magnetic field intensity, the magnetic domain rotation energy threshold ratio of the composite magnetoelectric material is determined, specifically: The magnetic energy at the preset first magnetic field strength on the rising hysteresis loop The expression is: ; In the formula, Represents the vacuum magnetic permeability, whose value is ; 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; Threshold ratio of magnetic domain rotation energy in composite magnetoelectric materials The expression is: ; It should be noted that the saturation magnetization is a well-known parameter in the hysteresis loop. The saturation magnetization refers to the maximum magnetization that a magnetic material can reach when it is magnetized in an external magnetic field. It can be obtained from material manuals and experimental tests. The value of the saturation magnetization in this embodiment is , the magnetization intensity at the preset first magnetic field intensity on the rising hysteresis loop is .

[0037] Among them, the vacuum permeability is a known parameter, and its value is .

[0038] According to the energy loss coefficient of the composite magnetoelectric material, it can be understood that the larger the magnetic energy at the preset first magnetic field strength, the closer it is to the theoretical magnetic energy, and the larger the magnetic domain rotation energy threshold ratio, which means that the magnetic domain needs a higher energy to start large-scale rotation, that is, the magnetic domain is restricted by a larger internal energy barrier, which may be due to the tight magnetic domain structure inside the material, the strong interaction between the magnetic domains, or the high anisotropy of the magnetic phase of the material. Therefore, the hysteresis effect will be more obvious at the beginning of the rotation of the magnetic domain, because the magnetic field strength needs to reach a higher value to enable the magnetic domain to overcome the energy threshold and start large-scale rotation, and during the rotation process, the magnetic domain will also show a strong hysteresis due to this higher energy limitation. On the contrary, the larger the magnetic energy at the preset first magnetic field strength, the greater the difference from the theoretical magnetic energy, and the smaller the magnetic domain rotation energy threshold ratio, which means that the hysteresis effect is relatively small at the beginning of the rotation of the magnetic domain, and the magnetic domain can respond to changes in the magnetic field strength in a relatively timely manner.

[0039] Step S4: 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.

[0040] Considering only the rotation of magnetic domains is not enough to reflect the hysteresis effect. The influence of phase interface also needs to be considered. In composite magnetoelectric materials, the phase interface is an important area in the process of magnetic domain movement. Due to the difference in lattice constants between different phases, energy conversion and loss will occur when the magnetic domain passes through the phase interface.

[0041] The lattice mismatch at the phase interface will cause the magnetic domains to be distorted when crossing the interface, thereby consuming energy. By studying the energy loss at the phase interface, we can deeply understand the influence of the complex microstructure of composite magnetoelectric materials on the hysteresis effect. Different phase composition, phase distribution and the properties of the phase interface will affect the behavior of the magnetic domains at the interface, and thus affect the hysteresis characteristics of the entire material.

[0042] The value of the preset second magnetic field strength is generally less than the magnetic field strength that makes the material reach the saturation magnetization strength, but it must be high enough to cover the process from the beginning of large-scale rotation of the magnetic domain to near saturation magnetization. When the magnetization intensity reaches the saturation magnetization intensity, the magnetic domains are almost all arranged in the direction of the magnetic field. Therefore, in this embodiment, the value of the preset second magnetic field strength is 0.8 times the magnetic field strength corresponding to the saturation magnetization intensity.

[0043] Further, 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 energy loss coefficient of the composite magneto-electric material is determined, specifically: 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; Further, 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 are obtained, and the frequency of the lattice vibration at the phase interface is identified by Raman spectroscopy; 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 the lattice vibration at the phase interface, the energy loss coefficient of the composite magnetoelectric material is determined, specifically: The expression of energy loss coefficient C of composite magnetoelectric material is: ; 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.

[0044] 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 between the ferromagnetic phase and the ferroelectric phase. The implementer may also use other methods to measure the difference between data, such as ratios. This embodiment does not impose any special restrictions on the selection of methods to measure the difference between data.

[0045] It should be understood that Represents the preset coefficient, which can be used to fit data by measuring materials with different lattice mismatch degrees. The value range is usually In this embodiment, the value is The implementer can also set it according to the specific situation, and this embodiment does not impose any special restrictions.

[0046] The process of using Raman spectroscopy to identify the frequency of lattice vibration at the phase interface is a well-known technique, and the specific steps are not described in detail.

[0047] According to the energy loss coefficient of composite magnetoelectric materials, it can be understood that the larger the energy loss coefficient is, the larger the proportion of energy loss at the phase interface in the total magnetic energy change is, and the phase interface plays a key role in the hysteresis process. It may be due to the large lattice mismatch at the phase interface, the larger the difference between the lattice constants, or the structure of the phase interface causes the magnetic domains to undergo greater distortion and energy dissipation when crossing. On the contrary, the smaller the energy loss coefficient is, the smoother the movement of the magnetic domains at the phase interface is during the change of magnetic field intensity, and the better the lattice matching of the phase interface is, that is, the smaller the difference between the lattice constants is, the less the hindrance of the interaction of the phase interface to the movement of the magnetic domains is, that is, the smaller the hysteresis effect is.

[0048] Step S5: Based on the rate of change of the slope of the hysteresis loop, the magnetic domain rotation energy threshold ratio and the energy loss coefficient, the hysteresis compensation factor of the composite magnetoelectric material is determined, and the compensating magnetization intensity at each magnetic field intensity on the rising hysteresis loop is determined in combination with the magnetization intensity at each magnetic field intensity; based on the difference between the magnetic field intensity at the upper limit of the preset magnetic field intensity range on the rising hysteresis loop and the preset first magnetic field intensity, and the difference between the compensating 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, the magnetoelectric coefficient of the composite magnetoelectric material is tested.

[0049] Based on the change rate of the slope of the hysteresis loop, the magnetic domain rotation energy threshold ratio and the energy loss coefficient, the hysteresis compensation factor of the composite magnetoelectric material is determined, 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, specifically: Hysteresis compensation factor of composite magnetoelectric materials The expression 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.

[0050] 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 magnetic domain rotation energy threshold ratio is larger, and the energy loss coefficient is larger, then the hysteresis compensation factor is larger, which means that the hysteresis effect is more serious and the impact on the calculation of the magnetoelectric coefficient of the composite magnetoelectric material is greater, so the magnetoelectric coefficient of the composite material should be compensated; on the contrary, if the rate of change of the slope of the hysteresis loop is smaller, the magnetic domain rotation energy threshold ratio is smaller, and the energy loss coefficient is smaller, then the hysteresis effect of the composite magnetoelectric material is smaller, so the compensation is also smaller.

[0051] Furthermore, the calculation of the magnetoelectric coefficient is compensated by the hysteresis compensation factor, so as to obtain a more accurate magnetoelectric coefficient. Specifically: First, each measured magnetization intensity is compensated using the magnetoelectric coefficient, specifically: The expression of the compensation magnetization intensity at each magnetic field strength on the rising hysteresis loop is: ; In the formula, It represents the compensation magnetization intensity at the magnetic field intensity i on the rising hysteresis loop; It represents the magnetization intensity at the magnetic field intensity i on the rising hysteresis loop.

[0052] Preferably, the schematic diagram of the compensation magnetization intensity acquisition process provided in this embodiment is as follows: Figure 3 shown.

[0053] Secondly, the magnetoelectric coefficient is calculated using the compensated magnetization intensity and the corresponding magnetic field intensity, specifically: Calculate the difference between the first magnetic field intensity on the preset 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 compensation magnetization intensity between the preset first magnetic field intensity of 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; The magnetoelectric coefficient of the composite magnetoelectric material is the ratio of the second difference to the first difference.

[0054] So far, this embodiment calculates the rate of change of the slope of the hysteresis curve by considering the influence of the initial magnetic domain rotation on the hysteresis curve; then calculates the magnetic domain rotation energy threshold ratio in combination with the magnetic energy at the turning point where the magnetic domain begins to rotate on a large scale; further, considers the influence of the energy loss caused by the magnetic domain rotation at the phase interface on the hysteresis effect, calculates the energy loss coefficient, and finally obtains the hysteresis compensation factor. The hysteresis compensation factor is calculated by considering the influence of the magnetic domain rotation of the internal microstructure of the composite magnetoelectric material on the hysteresis effect, and the magnetoelectric coefficient is further calculated by considering the hysteresis compensation factor, which can effectively reduce the interference of the hysteresis phenomenon on the measurement results, so that the calculated magnetoelectric coefficient is closer to the real magnetoelectric conversion performance of the material, and improves the measurement accuracy of the magnetoelectric coefficient of the composite magnetoelectric material.

[0055] It should be noted that, in the preset magnetic field strength range of this embodiment, the preset first magnetic field strength and the preset second magnetic field strength are all between the preset negative maximum magnetic field strength and the preset positive maximum magnetic field strength.

[0056] Based on the same inventive concept as the above method, an embodiment of the present application also provides 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, wherein 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.

[0057] It should be noted that the above sequence of the embodiments of the present application is for description only and does not represent the advantages and disadvantages of the embodiments. The above is a description of a specific embodiment of this specification. In addition, the processes depicted in the accompanying drawings do not necessarily require the specific order or continuous order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0058] The various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referenced to each other, and each embodiment focuses on the differences from other embodiments.

[0059] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions, improvements, etc. made within the principles of the present application should 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; Based on the change rate of the slope of the hysteresis loop, the magnetic domain rotation energy threshold ratio and the energy loss coefficient, the hysteresis compensation factor of the composite magnetoelectric material is determined, 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; 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 magnetoelectric 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 magnetic permeability of vacuum; 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 expression of the hysteresis compensation factor of the composite magnetoelectric material is: ; In the formula, represents the hysteresis compensation factor of the composite magnetoelectric material; R, P, 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.

7. A method for testing the magnetoelectric coefficient of a composite magnetoelectric material as claimed in claim 1, characterized in that: The expression of the compensation magnetization intensity at each magnetic field intensity on the rising hysteresis loop 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.

8. A method for testing the magnetoelectric coefficient of a composite magnetoelectric material as claimed in claim 1, characterized in that: The testing of the magnetoelectric coefficient of the composite magnetoelectric material comprises: 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.

9. A method for testing the magnetoelectric coefficient of a composite magnetoelectric material as claimed in claim 8, 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.

10. 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 9 is implemented.

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