A method and system for testing magnetization dynamic parameters and magnetic elastic coupling coefficients

Abstract

This invention relates to a method and system for testing magnetization dynamic parameters and magnetoelastic coupling coefficients, belonging to the field of magnetic material testing technology. The invention applies an external magnetic field to a two-port surface acoustic wave (SAW) delay line containing a magnetostrictive thin film under test. This alters the shear modulus of the SAW film, causing dispersion of the SAW wave velocity and consequently a phase change in the delay line. The magnitude of this shear modulus change is related to the high-frequency magnetization dynamic parameters and the magnetoelastic coupling coefficient, and also corresponds one-to-one with the phase change of the SAW delay line. By detecting the phase change, the high-frequency magnetization dynamic parameters and the magnetoelastic coupling coefficient of the SAW film can be deduced. This invention can extract the uniaxial anisotropic field, magnetoelastic coupling coefficient, and effective damping factor of the SAW film in a single operation. It is simple to operate and solves the problem of requiring separate testing of the magnetoelastic coupling coefficient in traditional methods.

Description

Technical Field

[0001] This invention belongs to the field of magnetic material testing technology, specifically relating to a testing method and system for magnetostrictive thin film materials, and in particular a testing method and system for magnetization dynamic parameters and magnetoelastic coupling coefficient. Background Technology

[0002] Magnetostrictive thin films have enormous application potential and value in novel magnetoelectric composite NEMS micro-antennas, ultra-high sensitivity surface acoustic wave magnetic field sensors, high-isolation microwave non-reciprocal devices, and ultra-low power spin-wave logic devices. In these high-frequency applications, the saturation magnetization, uniaxial anisotropic field strength, effective damping factor, and magnetoelastic coupling coefficient of magnetostrictive thin films are indispensable material parameters in device design.

[0003] Traditionally, the ferromagnetic resonance (FMR) frequencies and linewidths of magnetostrictive thin films under different applied magnetic fields can be measured using resonant cavities, coplanar waveguides, or microstrip lines combined with vector network analyzers, thereby calculating the saturation magnetization, uniaxial anisotropic field strength, and effective damping factor. However, micrometer-scale, patterned magnetostrictive thin films exhibit strong demagnetizing effects and edge magnetic domains, making them difficult to test using the above methods. More complex near-field microwave probes, magnetic force microscopes, or diamond color centers are required for localized FMR testing, which suffers from operational complexity and insufficient testing accuracy. Furthermore, the magnetoelastic coupling coefficient requires separate testing of the magnetostriction coefficient using the cantilever beam method, or the Young's modulus effect under different applied magnetic fields using the resonant-anti-resonant method. Summary of the Invention

[0004] To overcome the problems of complex operation and insufficient accuracy of current testing methods, this invention provides a method and system for testing magnetization dynamic parameters and magnetoelastic coupling coefficients. Based on surface acoustic wave (SAW) theory and magnetization dynamics theory, this invention utilizes the magneto-acoustic coupling effect to convert the intrinsic parameters of the magnetostrictive thin film into SAW wave velocity information. By acquiring the phase of the SAW electrical signal and processing the data, the uniaxial anisotropic field, magnetoelastic coupling coefficient, and effective damping factor of the magnetostrictive thin film are extracted in one step. Based on a SAW delay line platform, this invention leverages the characteristics of SAW transmission in the magnetostrictive thin film and its ability to be controlled by a magnetic field. It is simple to operate, has high testing accuracy, and is low in cost. It avoids external environmental interference introduced by other non-contact testing methods and has a higher signal-to-noise ratio.

[0005] The technical solution adopted by this invention to solve its technical problem is as follows:

[0006] A method for testing magnetization dynamics parameters and magnetoelastic coupling coefficients, based on a testing system, includes a gaussmeter, a DC power supply, a vector network analyzer, a coil, and a two-port surface acoustic wave delay line containing the magnetostrictive thin film under test. The method comprises the following steps:

[0007] Step 1. Test the transmission coefficient of the two-port surface acoustic wave delay line;

[0008] By changing the current value of the DC power supply, magnetic fields of different magnitudes are applied to the two-port surface acoustic wave delay line containing the magnetostrictive film under test in the direction perpendicular to the surface acoustic wave vector. The transmission coefficient of the surface acoustic wave delay line in the preset frequency band is tested, and the magnetic field value is tested by a gaussmeter at the same time. The correspondence between each magnetic field and the transmission coefficient in the preset frequency band under the corresponding magnetic field is obtained within the preset magnetic field range.

[0009] Step 2. Modal selection;

[0010] Extract the transmission coefficient within a preset frequency band under a saturated magnetic field to determine the fundamental mode and higher harmonic frequencies of the two-port surface acoustic wave delay line.

[0011] Step 3. Phase extraction;

[0012] Based on the transmission coefficients within the preset frequency bands under each magnetic field obtained in step 1, the phases of the fundamental mode and higher harmonics of the surface acoustic wave delay line under each magnetic field are extracted.

[0013] Step 4. Modulus Calculation:

[0014] Based on the phase calculated in step 3, and combined with the length and frequency of the magnetostrictive film under test in the direction of the surface acoustic wave vector, the wave velocity of the fundamental mode and higher harmonics of the surface acoustic wave delay line under each magnetic field is calculated.

[0015] Substituting the wave velocity into the dispersion relation of surface acoustic waves in multilayer media, the modulus of the corresponding harmonics under each magnetic field is obtained.

[0016] Step 5. Parameter fitting;

[0017] Step 5.1: Constructing the fitting relationship;

[0018] Construct a fitting relationship for the modulus of the magnetostrictive thin film to be tested;

[0019] Step 5.2 Uniaxial anisotropic field strength Magnetoelastic coupling coefficient and effective damping factor Calculation:

[0020] ,in The magnetic field corresponding to the maximum modulus of the magnetostrictive thin film under test;

[0021] ,in The modulus of the magnetostrictive thin film under the saturated magnetic field is given. The modulus of the fundamental mode under zero field conditions;

[0022] The moduli of the fundamental mode and higher harmonics under zero field are compared with the calculated values. and Substitute the fitting relationship constructed in step 5.1 into the fitting data to obtain the effective damping factor. .

[0023] Furthermore, in step 3, the phase of the fundamental mode and higher harmonics of the surface acoustic wave delay line under each magnetic field:

[0024]

[0025] in, , Represents magnetic field The phase corresponding to the lower harmonic, Represents magnetic field The real part of the transmission coefficient corresponding to the lower harmonic, Represents magnetic field The imaginary part of the transmission coefficient corresponding to the lower harmonic; magnetic field The value range is from 0 to the saturation magnetic field. ; 1 corresponds to the fundamental mode, 3 corresponds to the third harmonic, 5 corresponds to the fifth harmonic, 7 corresponds to the seventh harmonic, and so on.

[0026] Furthermore, in step 4, the wave velocities of the fundamental mode and higher harmonics of the surface acoustic wave delay line under each magnetic field are as follows:

[0027]

[0028] Dispersion relation of surface acoustic waves in multilayer media:

[0029]

[0030] in and The values ​​represent the surface acoustic wave velocity and density in the piezoelectric substrate of the surface acoustic wave delay line, respectively. and These represent the thickness and density of the magnetostrictive thin film to be tested, respectively. is the length of the magnetostrictive thin film under test in the direction of the surface acoustic wave vector; These are the frequencies of the fundamental mode and higher harmonics of the two-port surface acoustic wave delay line. ; 1 corresponds to the fundamental mode, 3 corresponds to the third harmonic, 5 corresponds to the fifth harmonic, 7 corresponds to the seventh harmonic, and so on;

[0031] Obtaining a magnetic field Modulus of the lower corresponding harmonic .

[0032] Furthermore, in step 5, the fitting relationship is:

[0033]

[0034] in, The modulus of the magnetostrictive thin film under test in a saturated magnetic field is given. The magnetoelastic coupling coefficient is... Let be the angle between the magnetic moment of the magnetostrictive thin film under test and the direction of the surface acoustic wave vector. The permeability of free space, The saturation magnetization is In-plane magnetic susceptibility:

[0035]

[0036] in The gyromagnetic ratio of the magnetostrictive thin film under test is given. Represents the imaginary unit. , The frequency of surface acoustic waves, For effective damping factor, , It is a magnetic field. For uniaxial anisotropic field strength, , Let be the wave velocity of the surface acoustic wave. The thickness of the magnetostrictive thin film to be measured is given.

[0037] Furthermore, the preset magnetic field range described in step 1 covers the saturated magnetic field of the magnetostrictive thin film under test. The magnetic field range up to 0.

[0038] Furthermore, the range of the preset frequency band mentioned in step 1 covers the frequency corresponding to the fundamental mode of the two-port surface acoustic wave delay line to the ferromagnetic resonance frequency of the magnetostrictive thin film under test.

[0039] A magnetization dynamics parameter and magnetoelastic coupling coefficient testing system includes a magnetic field generation and measurement subsystem, a transmission coefficient testing subsystem, a computer, and a two-port surface acoustic wave delay line containing a magnetostrictive thin film to be tested;

[0040] The magnetic field generation and measurement subsystem includes a Helmholtz coil, a DC power supply, and a gaussmeter, which generates and measures the magnetic field in the direction perpendicular to the surface acoustic wave vector of the two-port surface acoustic wave delay line containing the magnetostrictive film under test; the transmission coefficient testing subsystem includes a vector network analyzer and a coaxial cable, which tests the transmission coefficient of the two-port surface acoustic wave delay line containing the magnetostrictive film under test.

[0041] The computer is connected to a DC power supply, a gaussmeter, and a vector network analyzer to respectively control the magnetic field value, measure the magnetic field value, and control the preset frequency band.

[0042] Furthermore, the dual-port surface acoustic wave delay line containing the magnetostrictive film under test includes a piezoelectric substrate, the magnetostrictive film under test located on the upper surface of the piezoelectric substrate, and interdigital transducers located on both sides of the magnetostrictive film under test; the interdigital transducers include interdigital electrodes and busbars, the period of which satisfies the condition that the frequency of the fundamental mode of the dual-port surface acoustic wave delay line is lower than the ferromagnetic resonance frequency of the magnetostrictive film under test.

[0043] Furthermore, the length of the interdigitated electrode is 0.6 to 0.9 times the length of the magnetostrictive film to be tested.

[0044] Furthermore, the easy magnetization axis of the magnetostrictive thin film under test is parallel to the direction of the surface acoustic wave vector.

[0045] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0046] 1. This invention utilizes the magneto-acoustic coupling effect to extract the uniaxial anisotropic field, magnetoelastic coupling coefficient, and effective damping factor of a magnetostrictive thin film in one operation. The operation is simple and solves the problem that traditional methods require separate testing of the magnetoelastic coupling coefficient.

[0047] 2. This invention is based on a mature surface acoustic wave delay line platform. Compared with traditional testing methods using resonant cavities, coplanar waveguides, or microstrip lines combined with vector network analyzers, it can test the magnetization dynamic parameters of micron-scale, patterned magnetostrictive thin films with high accuracy and low cost.

[0048] 3. This invention converts the intrinsic parameters of the magnetostrictive film into surface acoustic wave velocity information. By acquiring the phase of the electrical signal of the surface acoustic wave, the magnetization dynamic parameters and magnetoelastic coupling coefficient of the magnetostrictive film are obtained. Compared with other non-contact tests, it can avoid interference from the external environment and has a higher test signal-to-noise ratio. Attached Figure Description

[0049] Figure 1 Flowchart of the method for testing magnetization dynamic parameters and magnetoelastic coupling coefficient provided by the present invention;

[0050] Figure 2 A schematic diagram of the magnetization dynamics parameter and magnetoelastic coupling coefficient testing system provided by the present invention;

[0051] Figure 3 A schematic diagram of a two-port surface acoustic wave delay line containing the magnetostrictive thin film under test in the magnetization dynamics parameter and magnetoelastic coupling coefficient testing system provided by the present invention;

[0052] Figure 4 The transmission coefficient of the two-port surface acoustic wave delay line in Example 1 The test results are shown in the image.

[0053] Figure 5 The diagram shows the phase results of the fundamental mode and higher harmonics of the surface acoustic wave delay line under different magnetic fields in Example 1.

[0054] Figure 6 The graph shows the calculated shear modulus of the FeCoSiB magnetostrictive film under different magnetic fields in Example 1.

[0055] Figure 7 The damping factor fitting results are for the FeCoSiB thin film of Example 1;

[0056] Figure 8 The transmission coefficient of the two-port surface acoustic wave delay line in Example 2 The test results are shown in the image.

[0057] Figure 9 The diagram shows the phase results of the fundamental mode and higher harmonics of the surface acoustic wave delay line under different magnetic fields in Example 2.

[0058] Figure 10 The graph shows the calculated shear modulus of the CoFeB magnetostrictive film under different magnetic fields in Example 2.

[0059] Figure 11 The damping factor fitting results are for the CoFeB magnetostrictive thin film of Example 2.

[0060] Among them, 11 is a computer, 2 is a two-port surface acoustic wave delay line containing the magnetostrictive thin film under test, 31 is a Helmholtz coil, 32 is a DC power supply, 33 is a gaussmeter, 41 is a vector network analyzer, 42 is a coaxial cable, 21 is a piezoelectric substrate, 22 is an interdigital transducer, 23 is the magnetostrictive thin film under test, 221 is an interdigital electrode, and 222 is a busbar. Detailed Implementation

[0061] The technical solution of the present invention will now be clearly and completely described in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments in this specification without creative effort are within the scope of protection of the present invention.

[0062] A method for testing magnetization dynamics parameters and magnetoelastic coupling coefficients, based on a testing system, includes a gaussmeter, a DC power supply, a vector network analyzer, a coil, and a two-port surface acoustic wave delay line containing the magnetostrictive thin film under test. The method comprises the following steps:

[0063] Step 1. Test the transmission coefficient of the two-port surface acoustic wave delay line;

[0064] By changing the current value of the DC power supply, magnetic fields of different magnitudes are applied to the two-port surface acoustic wave delay line containing the magnetostrictive film under test in the direction perpendicular to the surface acoustic wave vector. The transmission coefficient of the surface acoustic wave delay line in the preset frequency band is tested, and the magnetic field value is tested by a gaussmeter at the same time. The correspondence between each magnetic field and the transmission coefficient in the preset frequency band under the corresponding magnetic field is obtained within the preset magnetic field range.

[0065] Step 2. Modal selection;

[0066] Extracting saturated magnetic field Transmission coefficient within the preset frequency band Determine the frequency points of the fundamental mode and higher harmonics of the two-port surface acoustic wave delay line. , ;in, This represents the frequency point of the corresponding harmonic. Corresponding fundamental mode, Corresponding to the third harmonic, Corresponding to the fifth harmonic, Corresponding to the seventh harmonic…;

[0067] Step 3. Phase extraction;

[0068] Based on the transmission coefficients within the preset frequency bands under each magnetic field obtained in step 1 Test results, extract each magnetic field Phase of the fundamental mode and higher harmonics of the lower surface acoustic wave delay line:

[0069] (1)

[0070] in, , Represents magnetic field The phase corresponding to the lower harmonic, Represents magnetic field The real part of the transmission coefficient corresponding to the lower harmonic, Represents magnetic field The imaginary part of the transmission coefficient corresponding to the lower harmonic; magnetic field The value range is from 0 to the saturation magnetic field. ; 1 corresponds to the fundamental mode, 3 corresponds to the third harmonic, 5 corresponds to the fifth harmonic, 7 corresponds to the seventh harmonic, and so on;

[0071] Step 4. Modulus Calculation:

[0072] Based on the phase calculated in step 3, and combined with the length of the magnetostrictive thin film under test in the direction of the surface acoustic wave vector, Calculate the wave velocity of the fundamental mode and higher harmonics of the surface acoustic wave delay line under each magnetic field, and the frequency points:

[0073] (2)

[0074] Substituting this into the dispersion relation of surface acoustic waves in multilayer media:

[0075] (3)

[0076] in and The values ​​represent the surface acoustic wave velocity and density in the piezoelectric substrate of the surface acoustic wave delay line, respectively. and These represent the thickness and density of the magnetostrictive thin film to be tested, respectively.

[0077] According to formula (3), the magnetic field is obtained. Modulus of the lower corresponding harmonic ;magnetic field The value range is from 0 to the saturation magnetic field. ; 1 corresponds to the fundamental mode, 3 corresponds to the third harmonic, 5 corresponds to the fifth harmonic, 7 corresponds to the seventh harmonic, and so on;

[0078] Step 5. Parameter fitting;

[0079] 5.1 Construction of Fitting Relationships;

[0080] According to the dynamic magnetoelastic coupling theory, under magneto-acoustic coupling, the modulus of the magnetostrictive thin film under test is: and Functions:

[0081] (4)

[0082] in, The modulus of the magnetostrictive film under test is given by the saturated magnetic field (the modulus of the magnetostrictive film under test does not change with harmonics under the saturated magnetic field). The magnetoelastic coupling coefficient is... Let be the angle between the magnetic moment of the magnetostrictive thin film under test and the direction of the surface acoustic wave vector. The permeability of free space, Saturation magnetization (saturation magnetization) It does not change with the area of ​​the magnetostrictive film; data is obtained by testing large-area films using a vibrating sample magnetometer. The in-plane magnetic susceptibility is calculated using the following formula:

[0083] (5)

[0084] in The gyromagnetic ratio of the magnetostrictive thin film under test is given. Represents the imaginary unit. , The frequency of surface acoustic waves, For effective damping factor, , It is a magnetic field. For uniaxial anisotropic field strength, , Let be the wave velocity of the surface acoustic wave. The thickness of the magnetostrictive film to be measured;

[0085] 5.2 Uniaxial anisotropic field strength Magnetoelastic coupling coefficient and effective damping factor Calculation:

[0086] ,in The magnetic field corresponding to the maximum modulus of the magnetostrictive thin film under test;

[0087] ,in The modulus of the magnetostrictive film under test is given by the saturated magnetic field (the modulus of the magnetostrictive film under test does not change with harmonics under the saturated magnetic field). The modulus of the fundamental mode under zero field conditions;

[0088] The moduli of the fundamental mode and higher harmonics under zero field are compared with the calculated values. and Substituting into formula (4) and fitting, the effective damping factor is obtained. .

[0089] Furthermore, the preset magnetic field range mentioned in step 1 needs to cover the saturated magnetic field of the magnetostrictive thin film under test. To reach the 0 magnetic field range, it is necessary to ensure that all magnetic field values ​​within this preset magnetic field range are scanned.

[0090] Furthermore, the range of the preset frequency band mentioned in step 1 needs to cover the frequency corresponding to the fundamental mode of the two-port surface acoustic wave delay line up to the ferromagnetic resonance (FMR) frequency of the magnetostrictive thin film under test.

[0091] Furthermore, in step 4, finite element simulation software can be used to model the two-port surface acoustic wave delay line containing the magnetostrictive film to be tested, and simulate to obtain its two-dimensional mapping table of wave velocity-modulus, so as to avoid the complex calculation of formula (3) and improve the accuracy of parameter calculation.

[0092] A magnetization dynamics parameter and magnetoelastic coupling coefficient testing system includes a magnetic field generation and measurement subsystem, a transmission coefficient testing subsystem, a computer, and a two-port surface acoustic wave delay line containing a magnetostrictive thin film to be tested;

[0093] The magnetic field generation and measurement subsystem includes a Helmholtz coil, a DC power supply, and a gaussmeter, which generates and measures the magnetic field in the direction perpendicular to the surface acoustic wave vector of the two-port surface acoustic wave delay line containing the magnetostrictive film under test; the transmission coefficient testing subsystem includes a vector network analyzer and a coaxial cable, which tests the transmission coefficient of the two-port surface acoustic wave delay line containing the magnetostrictive film under test.

[0094] The computer is connected to a DC power supply, a gaussmeter, and a vector network analyzer to respectively control the magnetic field value, measure the magnetic field value, and control the preset frequency band.

[0095] Furthermore, the two-port surface acoustic wave delay line containing the magnetostrictive film under test includes a piezoelectric substrate, the magnetostrictive film under test located on the upper surface of the piezoelectric substrate, and interdigital transducers located on both sides of the magnetostrictive film under test; the interdigital transducers include interdigital electrodes and busbars, and their periods must satisfy the requirement that the frequency of the fundamental mode of the two-port surface acoustic wave delay line ( The ferromagnetic resonance (FMR) frequency below that of the magnetostrictive thin film under test (Based on existing literature or other tests).

[0096] Furthermore, the easy magnetization axis of the magnetostrictive thin film under test is parallel to the direction of the surface acoustic wave vector.

[0097] Furthermore, a two-port surface acoustic wave delay line containing a magnetostrictive thin film under test is used, which is capable of exciting horizontal shear surface acoustic wave modes.

[0098] This invention provides a method and system for testing magnetization dynamic parameters and magnetoelastic coupling coefficients. By applying an external magnetic field to a two-port surface acoustic wave delay line containing a magnetostrictive thin film under test, the shear modulus of the magnetostrictive thin film changes, causing dispersion of the surface acoustic wave velocity, which in turn leads to the delay line... Phase change. The magnitude of the change in the shear modulus of the magnetostrictive thin film under test is related to the high-frequency magnetization dynamic parameters and the magnetoelastic coupling coefficient, and also corresponds one-to-one with the phase change of the surface acoustic wave delay line. This can be achieved by detecting... The phase change can be used to deduce the high-frequency magnetization dynamics parameters and magnetoelastic coupling coefficient of the magnetostrictive thin film.

[0099] Figure 1 The flowchart of the magnetization dynamic parameters and magnetoelastic coupling coefficient testing method provided by the present invention includes five steps: transmission coefficient testing, mode selection, phase extraction, modulus calculation, and parameter fitting calculation.

[0100] Figure 2The schematic diagram of the magnetization dynamics parameter and magnetoelastic coupling coefficient testing system provided by the present invention includes a magnetic field generation and measurement subsystem, a transmission coefficient testing subsystem, a computer 11, and a two-port surface acoustic wave delay line 2 containing the magnetostrictive thin film to be tested;

[0101] The magnetic field generation and measurement subsystem includes a Helmholtz coil 31, a DC power supply 32, and a gaussmeter 33. The Helmholtz coil 31 is connected to the DC power supply 32, and the test probe end of the gaussmeter 33 is placed at the center of the Helmholtz coil 31. This subsystem realizes the generation and measurement of the magnetic field in the direction perpendicular to the surface acoustic wave vector of the two-port surface acoustic wave delay line 2 containing the magnetostrictive film to be tested.

[0102] The transmission coefficient testing subsystem includes a vector network analyzer 41 and a coaxial cable 42. The two-port surface acoustic wave delay line 2 containing the magnetostrictive film under test is connected to the vector network analyzer 41 using the coaxial cable 42 to realize the testing of the transmission coefficient of the two-port surface acoustic wave delay line containing the magnetostrictive film under test.

[0103] Computer 11 is connected to DC power supply 32, gaussmeter 33 and vector network analyzer 41 respectively, to realize the adjustment of magnetic field value, the measurement of magnetic field value and the adjustment of preset frequency band.

[0104] like Figure 3 As shown, the two-port surface acoustic wave delay line 2 containing the magnetostrictive film under test comprises three parts: a piezoelectric substrate 21, interdigital transducers 22, and the magnetostrictive film under test 23. The piezoelectric substrate 21 is made of ST-cut quartz, 42° Y-cut lithium tantalate (LiTaO3), 128° Y-cut lithium niobate (LiNbO3), 112° Y-cut lanthanum gallium silicate (LGS), etc. The interdigital transducers 22 consist of two sets located at both ends of the upper surface of the piezoelectric substrate, each comprising interdigital electrodes 221 and busbars 222. The length of a single interdigital electrode 221 is 0.6 to 0.9 times the length of the magnetostrictive film 23, and its period must satisfy the condition that the frequency of the fundamental mode of the two-port surface acoustic wave delay line ( The ferromagnetic resonance (FMR) frequency below that of the magnetostrictive thin film under test (Based on existing literature or other tests); the magnetostrictive thin film 23 to be tested is located between two sets of interdigital transducers 22, and is made of iron-silicon-boron (FeSiB), iron-cobalt-silicon-boron (FeCoSiB), iron-silicon-boron-carbon (FeSiBC), iron-gallium-boron (FeGaB), cobalt-iron-boron (CoFeB), nickel (Ni), etc., with a length and width of 100 ~ 5000 μm and a thickness of 10 ~ 200 nm. The easy magnetization axis of the magnetostrictive thin film 23 is parallel to the direction of the surface acoustic wave vector.

[0105] Example 1

[0106] In this embodiment, the piezoelectric substrate 21 is made of 42° Y-cut lithium tantalate with a thickness of 500 μm. The interdigital transducer 22 is made of metallic aluminum, with 5 cycles per transducer. The interdigital electrode 221 is 1000 μm long, 4 μm wide, and 50 nm thick. The magnetostrictive thin film 23 is made of (Fe... 90 Co 10 ) 78 Si 12 B 10 ,length It has a diameter of 1200 μm, a width of 1000 μm, and a thickness of [missing information]. It is 30 nm.

[0107] Step 1: Transmission Coefficient Test. By varying the current value, a magnetic field of -80 Oe to +80 Oe is applied to the two-port surface acoustic wave delay line 2 containing the magnetostrictive film under test in a direction perpendicular to the surface acoustic wave vector. The transmission coefficient is then tested in the range of 10 MHz to 2.1 GHz. Simultaneously measure the current magnetic field value Repeat this step until all required magnetic field values ​​have been scanned.

[0108] Step 2: Modality selection. For example... Figure 4 As shown, according to The test results show the frequency of the fundamental mode of the horizontal shear wave from the two-port surface acoustic wave delay line 2 containing the magnetostrictive thin film under test. It can also measure 7 higher harmonics.

[0109] Step 3: Phase extraction. For example... Figure 5 As shown, the result obtained through step 2 Extract each The phase of the fundamental mode and the 3rd to 15th harmonics.

[0110] Step 4: Modulus calculation. For example... Figure 6 As shown, the phase obtained in step 3, combined with the length of the magnetostrictive thin film... ,thickness ,density and Calculations are different Modulus of the magnetostrictive thin film.

[0111] Step 5: Parameter fitting calculation. First, as... Figure 6 As shown, the modulus curves of the magnetostrictive thin film under the fundamental mode and all higher harmonics are all... When the value reaches its maximum, we can obtain... After that, as Figure 6 As shown, the fundamental mode Zero field ,according to You can get Finally, as Figure 7 As shown, the moduli of the fundamental mode and higher harmonics under zero field are compared with the calculated values. and Substituting into formula (4) and fitting, the effective damping factor is obtained. .

[0112] Example 2

[0113] In this embodiment, the piezoelectric substrate 21 is made of 42° Y-cut lithium tantalate with a thickness of 500 μm. The interdigital transducer 22 is made of aluminum, with 5 cycles per transducer. The interdigital electrode 221 is 535 μm long, 2 μm wide, and 50 nm thick. The magnetostrictive thin film 23 is made of Co. 60 Fe 20 B 20 ,length It has a diameter of 635 μm, a width of 550 μm, and a thickness of 100 μm. It is 30 nm.

[0114] Step 1: Transmission coefficient test. By varying the current value, a magnetic field of -60 Oe to +60 Oe is applied to the two-port surface acoustic wave delay line 2 containing the magnetostrictive film under test in a direction perpendicular to the surface acoustic wave vector. The transmission coefficient is then tested in the range of 150 MHz to 2.6 GHz. Simultaneously measure the current magnetic field value Repeat this step until all required magnetic field values ​​have been scanned.

[0115] Step 2: Modality selection. For example... Figure 8 As shown, according to The test results show the frequency of the fundamental mode of the horizontal shear wave from the two-port surface acoustic wave delay line 2 containing the magnetostrictive thin film under test. It can also measure four higher harmonics.

[0116] Step 3: Phase extraction. For example... Figure 9 As shown, the result obtained through step 2 Extract each The phase of the fundamental mode and the 3rd to 9th harmonics.

[0117] Step 4: Modulus calculation. For example... Figure 10 As shown, the phase obtained in step 3, combined with the length of the magnetostrictive thin film... ,thickness ,density and Calculations are different Modulus of the magnetostrictive thin film.

[0118] Step 5: Parameter fitting calculation. First, as...Figure 10 As shown, the modulus curves of the magnetostrictive thin film under the fundamental mode and all higher harmonics are all... When the value reaches its maximum, we can obtain... After that, as Figure 10 As shown, the fundamental mode Zero field ,according to You can get Finally, as Figure 11 As shown, the moduli of the fundamental mode and higher harmonics under zero field are compared with the calculated values. and Substituting into formula (4) and fitting, the effective damping factor is obtained. .

Claims

1. A method for testing magnetization dynamic parameters and magnetoelastic coupling coefficient, characterized in that, The test system, comprising a gaussmeter, a DC power supply, a vector network analyzer, a coil, and a two-port surface acoustic wave delay line containing the magnetostrictive thin film under test, is implemented using the following steps: Step 1. Test the transmission coefficient of the two-port surface acoustic wave delay line; By changing the current value of the DC power supply, magnetic fields of different magnitudes are applied to the two-port surface acoustic wave delay line containing the magnetostrictive film under test in the direction perpendicular to the surface acoustic wave vector. The transmission coefficient of the surface acoustic wave delay line in the preset frequency band is tested, and the magnetic field value is tested by a gaussmeter at the same time. The correspondence between each magnetic field and the transmission coefficient in the preset frequency band under the corresponding magnetic field is obtained within the preset magnetic field range. Step 2. Modal selection; Extract the transmission coefficient within a preset frequency band under a saturated magnetic field to determine the fundamental mode and higher harmonic frequencies of the two-port surface acoustic wave delay line. Step 3. Phase extraction; Based on the transmission coefficients within the preset frequency bands under each magnetic field obtained in step 1, the phases of the fundamental mode and higher harmonics of the surface acoustic wave delay line under each magnetic field are extracted. Step 4. Modulus Calculation: Based on the phase calculated in step 3, and combined with the length and frequency of the magnetostrictive film under test in the direction of the surface acoustic wave vector, the wave velocity of the fundamental mode and higher harmonics of the surface acoustic wave delay line under each magnetic field is calculated. Substituting the wave velocity into the dispersion relation of surface acoustic waves in multilayer media, the modulus of the corresponding harmonics under each magnetic field is obtained. Step 5. Parameter fitting; Step 5.1: Constructing the fitting relationship; Construct a fitting relationship for the modulus of the magnetostrictive thin film to be tested; Step 5.2 Uniaxial anisotropic field strength Magnetoelastic coupling coefficient and effective damping factor Calculation: ,in The magnetic field corresponding to the maximum modulus of the magnetostrictive thin film under test; ,in The modulus of the magnetostrictive thin film under the saturated magnetic field is given. The modulus of the fundamental mode under zero field conditions; The moduli of the fundamental mode and higher harmonics under zero field are compared with the calculated values. and Substitute the fitting relationship constructed in step 5.1 into the fitting data to obtain the effective damping factor. .

2. The method for testing magnetization dynamic parameters and magnetoelastic coupling coefficient according to claim 1, characterized in that, In step 3, the phase of the fundamental mode and higher harmonics of the surface acoustic wave delay line under each magnetic field: in, , Represents magnetic field The phase corresponding to the lower harmonic, Represents magnetic field The real part of the transmission coefficient corresponding to the lower harmonic, Represents magnetic field The imaginary part of the transmission coefficient corresponding to the lower harmonic; magnetic field The value range is from 0 to the saturation magnetic field. ; 1 corresponds to the fundamental mode, 3 corresponds to the third harmonic, 5 corresponds to the fifth harmonic, 7 corresponds to the seventh harmonic, and so on.

3. The method for testing magnetization dynamic parameters and magnetoelastic coupling coefficient according to claim 1, characterized in that, In step 4, the wave velocities of the fundamental mode and higher harmonics of the surface acoustic wave delay line under each magnetic field are as follows: Dispersion relation of surface acoustic waves in multilayer media: in and The values ​​represent the surface acoustic wave velocity and density in the piezoelectric substrate of the surface acoustic wave delay line, respectively. and These represent the thickness and density of the magnetostrictive thin film to be tested, respectively. is the length of the magnetostrictive thin film under test in the direction of the surface acoustic wave vector; These are the frequencies of the fundamental mode and higher harmonics of the two-port surface acoustic wave delay line. ; 1 corresponds to the fundamental mode, 3 corresponds to the third harmonic, 5 corresponds to the fifth harmonic, 7 corresponds to the seventh harmonic, and so on; Obtaining a magnetic field Modulus of the lower corresponding harmonic .

4. The method for testing magnetization dynamic parameters and magnetoelastic coupling coefficient according to claim 1, characterized in that, In step 5, the fitting relationship is: in, The modulus of the magnetostrictive thin film under test in a saturated magnetic field is given. The magnetoelastic coupling coefficient is... Let be the angle between the magnetic moment of the magnetostrictive thin film under test and the direction of the surface acoustic wave vector. The permeability of free space, The saturation magnetization is In-plane magnetic susceptibility: in The gyromagnetic ratio of the magnetostrictive thin film under test is given. Represents the imaginary unit. , The frequency of surface acoustic waves, For effective damping factor, , It is a magnetic field. For uniaxial anisotropic field strength, , Let be the wave velocity of the surface acoustic wave. The thickness of the magnetostrictive thin film to be measured is given.

5. The method for testing magnetization dynamic parameters and magnetoelastic coupling coefficient according to claim 1, characterized in that, The preset magnetic field range described in step 1 covers the saturated magnetic field of the magnetostrictive thin film under test. The magnetic field range up to 0.

6. The method for testing magnetization dynamic parameters and magnetoelastic coupling coefficient according to claim 1, characterized in that, The range of the preset frequency band in step 1 covers the frequency corresponding to the fundamental mode of the two-port surface acoustic wave delay line to the ferromagnetic resonance frequency of the magnetostrictive thin film under test.

7. A system for testing magnetization dynamic parameters and magnetoelastic coupling coefficient, characterized in that, It includes a magnetic field generation and measurement subsystem, a transmission coefficient testing subsystem, a computer, and a two-port surface acoustic wave delay line containing the magnetostrictive thin film under test; The magnetic field generation and measurement subsystem includes a Helmholtz coil, a DC power supply, and a gaussmeter, which generates and measures the magnetic field in the direction perpendicular to the surface acoustic wave vector of the two-port surface acoustic wave delay line containing the magnetostrictive film under test; the transmission coefficient testing subsystem includes a vector network analyzer and a coaxial cable, which tests the transmission coefficient of the two-port surface acoustic wave delay line containing the magnetostrictive film under test. The computer is connected to a DC power supply, a gaussmeter, and a vector network analyzer to respectively control the magnetic field value, measure the magnetic field value, and control the preset frequency band.

8. The magnetization dynamics parameter and magnetoelastic coupling coefficient testing system according to claim 7, characterized in that, The dual-port surface acoustic wave delay line containing the magnetostrictive film under test includes a piezoelectric substrate, the magnetostrictive film under test located on the upper surface of the piezoelectric substrate, and interdigital transducers located on both sides of the magnetostrictive film under test. The interdigital transducers include interdigital electrodes and busbars, and their periods are such that the frequency of the fundamental mode of the dual-port surface acoustic wave delay line is lower than the ferromagnetic resonance frequency of the magnetostrictive film under test.

9. The magnetization dynamics parameter and magnetoelastic coupling coefficient testing system according to claim 7, characterized in that, The length of the interdigitated electrode is 0.6 to 0.9 times the length of the magnetostrictive film to be tested.

10. The magnetization dynamics parameter and magnetoelastic coupling coefficient testing system according to claim 7, characterized in that, The easy magnetization axis of the magnetostrictive thin film under test is parallel to the direction of the surface acoustic wave vector.

Images