System and method for testing extremely narrow ferromagnetic resonance line width based on rectangular coaxial cavity

Abstract

The invention provides a system and a method for testing extremely narrow ferromagnetic resonance line width of a spherical sample based on a rectangular coaxial resonant cavity, and belongs to the technical field of microwave and millimeter wave testing. According to the test system, a rectangular coaxial resonant cavity is designed as a test core device, and an inner conductor and an outer conductor are in direct contact and are coaxial, so that the rectangular coaxial resonant cavity structure forms an approximately uniform magnetic field in an area for placing a sample, and the structure can avoid the situation of inaccurate test caused by anisotropy of the spherical sample; and the volume of the measurable spherical sample of the rectangular coaxial resonant cavity can be larger, so that the preparation and characterization difficulty of the sample is reduced, and the measurement accuracy is improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of microwave and millimeter wave testing, and particularly relates to a system and method for testing extremely narrow ferromagnetic resonance line width based on a rectangular coaxial cavity. BACKGROUND

[0002] In the middle of last century, the discovery and application of microwave ferrite materials was a major breakthrough in the field of microwave technology. Today, using the gyromagnetic properties of ferrite, a variety of key microwave devices such as phase shifters, circulators and isolators can be developed. In the design and application of ferrite materials, the ferromagnetic resonance line width is one of the most basic and important characteristic parameters, which directly determines the values of the components of the tensor permeability in the ferromagnetic resonance frequency band. With the continuous improvement of system integration, higher requirements are put forward for the quality of raw materials, especially the need for materials to have extremely low loss characteristics, which makes it an urgent need to accurately measure the extremely narrow ferromagnetic resonance line width.

[0003] When measuring the extremely narrow ferromagnetic resonance line width, using a large-size spherical sample has significant advantages: on the one hand, it can effectively suppress the surface effect, thus more accurately obtaining the intrinsic damping and uniformity information of the bulk material; on the other hand, the spherical sample can eliminate the influence of shape anisotropy, making the internal magnetization response more consistent in a uniform microwave field, which is conducive to reflecting the true physical properties of the material. Therefore, developing a ferromagnetic resonance test system that can be applied to large-size spherical samples and accurately measure the extremely narrow line width not only helps to improve the measurement accuracy of the intrinsic parameters of the material, but also reduces the measurement error introduced by the non-ideal shape of the sample, which has important scientific research and engineering value.

[0004] In current research, the mainstream test methods are divided into two types: the perturbation method of resonant cavity and the broadband transmission line measurement method. Among them, the perturbation method of resonant cavity is mainly applied to the test of yttrium iron garnet (YIG) single crystal small balls, lithium ferrite (LiFe), manganese ferrite (MnFe) and other spherical samples. Although the measurement accuracy is high, the magnetic field in the resonant cavity is not uniform, which excites the anisotropy of the small sample balls, resulting in double peaks during testing and affecting the accuracy of the test. For example, Fang Qingyu mentioned in the paper "Ferromagnetic Resonance Line Width Test Research Based on Electromagnetic Simulation" that when the sample size is too large, the resonance curve begins to collapse and double peaks appear, indicating that the sample at this time does not meet the perturbation theory. Tang Kun designed an iron magnetic resonance line width test system in the paper "Full-band magnetic thin film / powder ferromagnetic resonance line width test system" by using a grounded coplanar waveguide and a rectangular resonant cavity waveguide structure. When testing samples with narrow line width, the coupling between the cavity and the sample exceeds the limit, resulting in a decrease in the quality factor of the perturbation resonant cavity and the appearance of double peaks, which affects the test results.

[0005] Coaxial resonant cavity has been widely used in the measurement of material electromagnetic parameters due to its open structure and clear field distribution. The principle of this method is to deduce the permittivity and permeability by the resonant frequency shift and Q value change caused by the sample. However, this method is difficult to be directly applied to the accurate measurement of ferromagnetic resonance linewidth, mainly because the ferromagnetic resonance measurement has extremely strict requirements on the uniformity and directionality of the magnetic field, while the annular magnetic field distribution of the coaxial cavity cannot provide the required high uniformity and plane polarization magnetic field at the sample as the traditional rectangular cavity, resulting in distortion of the resonance peak shape and decrease of the linewidth test accuracy.

[0006] Therefore, it is of great practical significance to design a test system for material resonance linewidth based on a coaxial resonant cavity, which can be applied to the test of large-volume samples and extremely narrow resonance linewidth. SUMMARY

[0007] In view of the problems in the background art, the purpose of the present application is to provide a test system and method for extremely narrow ferromagnetic resonance linewidth of a spherical sample based on a rectangular coaxial resonant cavity. The test system designs a rectangular coaxial resonant cavity as the core test device. The inner conductor and the outer conductor are in direct contact and coaxial, so that the rectangular coaxial resonant cavity structure forms an approximately uniform magnetic field in the area where the sample is placed. This structure can avoid the situation that the test is not accurate due to the anisotropy of the spherical sample. Moreover, the volume of the spherical sample that can be measured by the rectangular coaxial resonant cavity can be larger, which reduces the difficulty of sample preparation and characterization and increases the accuracy of measurement.

[0008] To achieve the above-mentioned purpose, the technical solutions of the present application are as follows:

[0009] The test system for extremely narrow ferromagnetic resonance linewidth of a spherical sample based on a rectangular coaxial resonant cavity comprises a rectangular coaxial resonant cavity 1, a coupling ring 3, a Helmholtz coil 4, an electromagnet 5, a gauss meter 6, a first power supply 7, an operation processing control unit 8, a vector network analyzer 9 and a second power supply 10.

[0010] The rectangular coaxial resonant cavity 1 comprises an outer conductor and an inner conductor which are both made of metal. The outer conductor is a hollow cuboid. The inner conductor is a solid cuboid. The inner conductor is arranged in the outer conductor, and the central axes of the two are kept coincident to form a coaxial cavity. The opposite end faces of the inner conductor are in direct contact with the opposite inner walls of the outer conductor. Symmetrical coupling holes 2 are formed on the opposite side walls of the outer conductor. The coupling holes have a certain vertical distance from the contact surfaces of the inner and outer conductors, and the coupling holes are away from the sample to be measured. The coupling ring 3 is fixedly arranged in the rectangular coaxial resonant cavity through the coupling holes.

[0011] A rectangular coaxial resonant cavity 1 is placed at the center of a Helmholtz coil 4; the Helmholtz coil 4 is placed at a location where the magnetic field of the electromagnet 5 is uniform; a first power supply 7 is used to power the Helmholtz coil, and a second power supply 10 is used to power the electromagnet 5; a gaussmeter 6 is used to measure the magnetic field generated by the electromagnet; a vector network analyzer 9 is connected to a coupling loop 3; and an arithmetic processing control unit 8 is connected to the vector network analyzer 9, the gaussmeter 6, the first power supply 7, and the second power supply 10 for data transmission and control.

[0012] Furthermore, the rectangular coaxial resonant cavity operates in TEM 00p The mode, p, represents the half-wave number of the electromagnetic field distribution along the longitudinal direction of the cavity.

[0013] Furthermore, the material to be tested is a spherical sample, which is placed between the inner and outer conductors and close to the contact surface between the inner and outer conductors.

[0014] Furthermore, by adjusting the cavity size and operating mode of the rectangular coaxial resonant cavity 1, the test frequency of the resonant linewidth measurement system can be adjusted.

[0015] Furthermore, the vertical distance between the coupling hole and the contact surface of the inner and outer conductors is preferably 1 mm.

[0016] Furthermore, the first power supply 7 is used to provide low-power power of up to 100W, and the second power supply 10 is used to provide high-power power of over 1000W.

[0017] The present invention also provides a measurement method based on the above-described testing system, comprising the following steps:

[0018] Step 1. Set up a test system, energize the Helmholtz coil, change the current through the Helmholtz coil, and use a gaussmeter to measure the magnetic field strength generated by the Helmholtz coil. With the distance from the placement position to the midpoint of the line connecting the center of the Helmholtz coil to the center of the coil, the number of coil turns, and the coil radius constant, the current-magnetic field strength relationship function of the Helmholtz coil is a linear function. Fit the current-magnetic field strength relationship function of the coil as follows:

[0019]

[0020] in, The magnetic field generated by the Helmholtz coil. Let be the current flowing through the Helmholtz coil, and 'a' be the fitting coefficient.

[0021] Step 2. Calibrate the ports of the vector network analyzer, complete the initialization settings of the vector network analyzer, and scan the rectangular coaxial resonant cavity TEM. 00p Find the peak value of the S21 curve using the pattern.

[0022] Step 3. Place the material to be tested into the rectangular coaxial resonant cavity and record the peak value of the S21 curve on the vector network analyzer after the sample is loaded;

[0023] Step 4. Power on the electromagnet, adjust the second power supply 10, gradually increase the power supply current, and adjust the magnitude of the static magnetic field strength generated by the electromagnet until the peak value of the S21 curve on the vector network analyzer drops to the minimum value at this time. Use a gaussmeter to measure the magnitude of the magnetic field strength generated by the electromagnet.

[0024] Step 5. Adjust the first power supply and adjust the magnitude of the static magnetic field generated by the Helmholtz coil until the peak value of the S21 curve on the vector network analyzer drops to the current minimum value. Record the current of the low power supply and the peak value of S21, and calculate the half-power point transfer coefficient S21half.

[0025] The formula for calculating the half-power point transmission factor S21half is as follows:

[0026]

[0027] Wherein, S210 is the peak value of S21 measured after loading the sample in step 3, and S21c is the peak value of S21 measured at the ferromagnetic resonance point when loading the sample and energizing the electromagnet and Helmholtz coil in step 5.

[0028] Step 6. Decrease the current of the first power supply until the peak value of the resonance peak S21 rises to S21half, and record the current I1 of the first power supply at this time; then gradually increase the current of the first power supply until the peak value of the resonance peak S21 rises to S21half, and record the current I2 of the first power supply at this time.

[0029] Step 7. Based on the current-magnetic field strength relationship function of the coil obtained in Step 1 and the currents I1 and I2 recorded in Step 6, calculate the magnitudes H1 and H2 of the magnetic field strength generated by the Helmholtz coil. Then, derive the ferromagnetic resonance linewidth of the spherical sample according to the definition of ferromagnetic resonance linewidth:

[0030]

[0031] H1 and H2 are the total magnetic field strengths at the half-power point, which include the static magnetic field strength generated by the electromagnet measured in step 4 and the static magnetic field strength generated by the Helmholtz coil.

[0032] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0033] This invention provides a testing system based on a rectangular coaxial resonant cavity for accurately measuring the ferromagnetic resonance linewidth of spherical samples. Compared to traditional cylindrical or rectangular resonant cavities, this invention innovatively utilizes a rectangular coaxial resonant cavity in specific TEM...00p In this mode, a highly uniform microwave magnetic field is generated in the central region along the wide side. Since the cavity width in the testing direction is much larger than the size of the spherical sample, a highly consistent magnetic field distribution is ensured throughout the sample area. This uniform magnetic field environment allows all magnetic moments within the spherical sample to precess synchronously, reducing the asynchronous magnetic moment response caused by magnetic field gradients and avoiding "double peaks" in the resonance spectrum. This results in a single, sharp resonance peak that truly reflects the intrinsic properties of the material. Based on this, the system demonstrates superior measurement capabilities for extremely narrow linewidth and large-size spherical samples: the uniform field effectively eliminates some of the spectral broadening introduced by field inhomogeneity, accurately characterizing the intrinsic low loss of the material; simultaneously, the wide cavity design allows for the use of large-size spherical samples, effectively suppressing surface effects and more realistically characterizing the bulk properties of the material, while achieving high-precision measurements without relying on ideally small spheres that are difficult to fabricate. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the overall test system for the extremely narrow ferromagnetic resonance linewidth of the present invention.

[0035] Figure 2 This is a schematic diagram of the rectangular coaxial resonant cavity in the testing system for the extremely narrow ferromagnetic resonance linewidth of this invention.

[0036] Figure 3 TEM of the rectangular coaxial resonant cavity in the test system of this invention 005 The magnetic field strength vector distribution diagram under the mode and the magnetic field strength vector distribution of the 16mm*8mm*5mm cuboid region around the spherical sample.

[0037] Figure 4 The simulation results of different testing systems on spherical samples with different ferromagnetic resonance linewidths and a radius of 0.5 mm are shown in the figure.

[0038] Wherein, (a) is the test system of the present invention, (b) is a rectangular resonant cavity, and (c) is a cylindrical high-Q resonant cavity.

[0039] Figure 5 The figure shows the simulation results of different testing systems for spherical samples of different sizes with a ferromagnetic resonance linewidth of 18 Oe.

[0040] Wherein, (a) is the test system of the present invention, (b) is a rectangular resonant cavity, and (c) is a cylindrical high-Q resonant cavity.

[0041] Figure reference numerals: 1 is a rectangular coaxial resonant cavity, 4 is a Helmholtz coil, 5 is an electromagnet, 6 is a gaussmeter, 7 is a low-power power supply, 8 is a computer, 9 is a vector network analyzer, and 10 is a high-power power supply. The computer 8 programs and controls the gaussmeter 6, the low-power power supply 7, the vector network analyzer 9, and the high-power power supply 10. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings.

[0043] A test system for spherical samples with extremely narrow ferromagnetic resonance linewidth based on a rectangular coaxial resonant cavity is shown in the overall schematic diagram below. Figure 1 As shown, it includes a rectangular coaxial resonant cavity 1, a coupling ring 3, a Helmholtz coil 4, an electromagnet 5, a gaussmeter 6, a first power supply 7, an arithmetic processing and control unit 8, a vector network analyzer 9, and a second power supply 10;

[0044] A schematic diagram of the rectangular coaxial resonant cavity 1 is shown below. Figure 2 As shown, the device includes an outer conductor and an inner conductor, both made of metal. The outer conductor is a hollow cuboid with openings on two opposite sidewalls for easy layout. The inner conductor is a solid cuboid, positioned inside the outer conductor with their central axes aligned to form a coaxial cavity. The opposite end faces of the inner conductor are in direct contact with the opposite inner walls of the outer conductor. Symmetrical coupling holes 2 are formed on the opposite sidewalls of the outer conductor. These coupling holes are at a certain perpendicular distance from the contact surfaces of the inner and outer conductors and are far from the sample to be tested. A coupling ring 3 is fixedly positioned within the rectangular coaxial cavity through the coupling holes.

[0045] A rectangular coaxial resonant cavity 1 is placed at the center of a Helmholtz coil 4; the Helmholtz coil 4 is placed at a location where the magnetic field of the electromagnet 5 is uniform; a first power supply 7 is used to power the Helmholtz coil, and a second power supply 10 is used to power the electromagnet 5; a gaussmeter 6 is used to measure the magnetic field generated by the electromagnet; a vector network analyzer 9 is connected to a coupling loop 3; and an arithmetic processing control unit 8 is connected to the vector network analyzer 9, the gaussmeter 6, the first power supply 7, and the second power supply 10 for data transmission and control.

[0046] Figure 3 TEM of the rectangular coaxial resonant cavity in the test system of this invention 005 The magnetic field strength vector distribution diagram in the mode is shown. The magnified area represents the magnetic field strength vector distribution within a 16mm*8mm*5mm cuboid region surrounding the spherical sample. The small sphere in the diagram represents the spherical sample, and the magnetic field distribution is uniform. The rectangular coaxial resonant cavity of this invention differs fundamentally from the conventional re-entry stripline resonant cavity. This is because the rectangular coaxial resonant cavity is a half-wavelength resonance with both ends short-circuited, while the re-entry stripline resonant cavity is a quarter-wavelength resonance with one end short-circuited and the other open.

[0047] Example 1

[0048] A testing system for spherical samples with extremely narrow ferromagnetic resonance linewidth based on a rectangular coaxial resonant cavity includes the following steps:

[0049] Step 1. Construct the experimental system. The outer conductor of the rectangular coaxial resonant cavity 1 is a hollow cuboid with a top surface, a bottom surface, a left side wall, and a right side wall. Its cavity width is 24 mm, length is 80 mm, height is 80 mm, and wall thickness is 5 mm. The inner conductor has a width of 8 mm, a length of 15 mm, and a height of 80 mm. Symmetrical coupling holes are formed on the left and right side walls of the outer metal conductor, 1 mm from the cavity bottom. The rectangular coaxial resonant cavity operates in TEM mode. 005 The frequency in this mode is approximately 9.348 GHz;

[0050] Step 2. Current is passed through the Helmholtz coil. By varying the current flowing through the coil, the magnetic field strength generated by the Helmholtz coil is measured using a gaussmeter.

[0051] The relationship between current and magnetic field strength in a Helmholtz coil is a linear function. The relationship between current and magnetic field strength in the coil can be fitted using the following method:

[0052]

[0053] in, The magnetic field generated by the Helmholtz coil. Let be the current flowing through the Helmholtz coil, and 'a' be the fitting coefficient.

[0054] Step 3. Calibrate the ports of the vector network analyzer, complete the initialization settings of the vector network analyzer, and scan the rectangular coaxial resonant cavity TEM. 005 model;

[0055] Step 4. Place the material to be tested into the rectangular coaxial resonant cavity and record the peak value of the S21 curve on the vector network analyzer after the sample is loaded;

[0056] Step 5. Power on the electromagnet, adjust the second power supply 10, gradually increase the power supply current, and adjust the magnitude of the static magnetic field strength generated by the electromagnet until the peak value of the S21 curve on the vector network analyzer drops to the minimum value at this time. Use a gaussmeter to measure the magnitude of the magnetic field strength generated by the electromagnet.

[0057] Step 6. Adjust the first power supply and adjust the magnitude of the static magnetic field generated by the Helmholtz coil until the peak value of the S21 curve on the vector network analyzer drops to the minimum value. Record the current of the low power supply, the peak value of S21, and obtain the half-power point transfer coefficient S21half.

[0058] Step 7. Decrease the current of the first power supply until the peak value of the resonance peak S21 rises to S21half, and record the current I1 of the first power supply at this time; then gradually increase the current of the first power supply until the peak value of the resonance peak S21 rises to S21half, and record the current I2 of the first power supply at this time.

[0059] The formula for calculating the half-power point transmission factor S21half is as follows:

[0060]

[0061] Wherein, S210 is the peak value of S21 measured after loading the sample in step 3, and S21c is the peak value of S21 measured at the ferromagnetic resonance point when loading the sample and energizing the electromagnet and Helmholtz coil in step 6.

[0062] Step 8. Based on the current-magnetic field strength relationship function obtained in Step 1, calculate the magnitude of the magnetic field strength generated by the Helmholtz coil, and derive the ferromagnetic resonance linewidth of the spherical sample according to the definition of ferromagnetic resonance linewidth:

[0063]

[0064] H1 and H2 are the total magnetic field strengths at the half-power point, which include the static magnetic field strength generated by the electromagnet measured in step 4 and the static magnetic field strength generated by the Helmholtz coil.

[0065] Figure 4 The figure shows the simulation results of the test system of this invention, the rectangular resonant cavity, and the cylindrical high-Q resonant cavity on a spherical sample with a radius of 0.5 mm. The horizontal axis represents frequency, and the vertical axis represents S21. As can be seen from the figure, under the same sample size, the rectangular coaxial resonant cavity only begins to show a critical double peak when testing a spherical sample with a ferromagnetic resonance linewidth of 10 Oe. When testing ferromagnetic resonance linewidths of 18 Oe and 31 Oe, both show a single peak. In contrast, the rectangular cavity and the cylindrical high-Q cavity show obvious double peaks when testing a spherical sample with a ferromagnetic resonance linewidth of 10 Oe. This indicates that the rectangular coaxial cavity of this invention can measure a significantly lower linewidth for spherical samples than the rectangular resonant cavity and the cylindrical high-Q resonant cavity.

[0066] Figure 5 The figures show the simulation results of testing a spherical sample with a ferromagnetic resonance linewidth of 18 Oe using the testing system of this invention, a rectangular resonant cavity, and a cylindrical high-Q resonant cavity. It can be seen that, under the same ferromagnetic resonance linewidth, the rectangular coaxial resonant cavity exhibits a critical double peak when testing a spherical sample with a radius of 0.69 mm, while both show a single peak when testing spherical samples with radii of 0.35 mm and 0.5 mm. In contrast, the rectangular cavity and the cylindrical high-Q cavity show obvious double peaks when testing a spherical sample with a radius of 0.69 mm. This indicates that, compared to the rectangular resonant cavity and the cylindrical high-Q resonant cavity, the rectangular coaxial resonant cavity can measure large-sized spherical samples without exhibiting double peaks, demonstrating that the testing system of this invention can reduce the difficulty of preparing spherical samples.

[0067] The above description is merely a specific embodiment of the present invention. Any feature disclosed in this specification may be replaced by other equivalent or similar features unless otherwise specified. All disclosed features, or steps in all methods or processes, may be combined in any way except for mutually exclusive features and / or steps.

Claims

1. A testing system for spherical samples with extremely narrow ferromagnetic resonance linewidths based on a rectangular coaxial resonant cavity, characterized in that, It includes a rectangular coaxial resonant cavity, a coupling ring, a Helmholtz coil, an electromagnet, a gaussmeter, a first power supply, a computational processing and control unit, a vector network analyzer, and a second power supply; The rectangular coaxial resonant cavity includes an outer conductor and an inner conductor, both made of metal. The outer conductor is a hollow cuboid, and the inner conductor is a solid cuboid. The inner conductor is placed inside the outer conductor, and their central axes coincide to form a coaxial cavity. The opposite end faces of the inner conductor are in direct contact with the opposite inner walls of the outer conductor. Coupled holes are symmetrically opened on the opposite side walls of the outer conductor. The coupled holes are at a certain perpendicular distance from the contact surfaces of the inner and outer conductors and are far away from the sample to be tested. A coupling ring is fixedly installed inside the rectangular coaxial cavity through the coupled holes. A rectangular coaxial resonant cavity is placed at the center of a Helmholtz coil; the Helmholtz coil is placed at a location where the electromagnet's magnetic field is uniform; a first power supply powers the Helmholtz coil, and a second power supply powers the electromagnet; a gaussmeter measures the magnetic field generated by the electromagnet; a vector network analyzer is connected to a coupling loop, and the computational processing control unit is connected to the vector network analyzer, the gaussmeter, the first power supply, and the second power supply for data transmission and control.

2. The testing system for extremely narrow ferromagnetic resonance linewidth of spherical samples based on a rectangular coaxial resonant cavity as described in claim 1, characterized in that, The rectangular coaxial resonator operates in TEM 00p The mode, p, represents the half-wave number of the electromagnetic field distribution along the longitudinal direction of the cavity.

3. The testing system for extremely narrow ferromagnetic resonance linewidth of spherical samples based on a rectangular coaxial resonant cavity as described in claim 1, characterized in that... The material to be tested is a spherical sample, which is placed between the inner and outer conductors and close to the contact surface between the inner and outer conductors.

4. The testing system for extremely narrow ferromagnetic resonance linewidth of spherical samples based on a rectangular coaxial resonant cavity as described in claim 1, characterized in that, The test frequency of the resonant linewidth measurement system can be adjusted by modifying the cavity size and operating mode of the rectangular coaxial resonant cavity.

5. The testing system for extremely narrow ferromagnetic resonance linewidth of spherical samples based on a rectangular coaxial resonant cavity as described in claim 1, characterized in that, The vertical distance between the coupling hole and the contact surface of the inner and outer conductors is 1 mm.

6. The testing system for extremely narrow ferromagnetic resonance linewidth of spherical samples based on a rectangular coaxial resonant cavity as described in claim 1, characterized in that, The first power supply 7 is used to provide low-power power up to 100W, and the second power supply 10 is used to provide high-power power up to 1000W.

7. A measurement method based on a test system for an extremely narrow ferromagnetic resonance linewidth of a spherical sample using a rectangular coaxial resonant cavity as described in any one of claims 1-6, characterized in that, Includes the following steps: Step 1. Set up a test system, energize the Helmholtz coil, change the current through the Helmholtz coil, and use a gaussmeter to measure the magnetic field strength generated by the Helmholtz coil. With the distance from the placement position to the midpoint of the line connecting the center of the Helmholtz coil to the center of the coil, the number of coil turns, and the coil radius constant, the current-magnetic field strength relationship function of the Helmholtz coil is a linear function. Fit the current-magnetic field strength relationship function of the coil as follows: ， in, The magnetic field generated by the Helmholtz coil. Let be the current flowing through the Helmholtz coil, and 'a' be the fitting coefficient. Step 2. Calibrate the ports of the vector network analyzer, complete the initialization settings of the vector network analyzer, and scan the rectangular coaxial resonant cavity TEM. 00p Find the peak value of the S21 curve using the pattern. Step 3. Place the material to be tested into the rectangular coaxial resonant cavity and record the peak value of the S21 curve on the vector network analyzer after the sample is loaded; Step 4. Power on the electromagnet, adjust the second power supply 10, gradually increase the power supply current, and adjust the magnitude of the static magnetic field strength generated by the electromagnet until the peak value of the S21 curve on the vector network analyzer drops to the minimum value at this time. Use a gaussmeter to measure the magnitude of the magnetic field strength generated by the electromagnet. Step 5. Adjust the first power supply and adjust the magnitude of the static magnetic field generated by the Helmholtz coil until the peak value of the S21 curve on the vector network analyzer drops to the current minimum value. Record the current of the low power supply and the peak value of S21, and calculate the half-power point transfer coefficient S21half. Step 6. Decrease the current of the first power supply until the peak value of the resonance peak S21 rises to S21half, and record the current I1 of the first power supply at this time; then gradually increase the current of the first power supply until the peak value of the resonance peak S21 rises to S21half, and record the current I2 of the first power supply at this time. Step 7. Based on the current-magnetic field strength relationship function of the coil obtained in Step 1 and the currents I1 and I2 recorded in Step 6, calculate the magnitudes H1 and H2 of the magnetic field strength generated by the Helmholtz coil. Then, derive the ferromagnetic resonance linewidth of the spherical sample according to the definition of ferromagnetic resonance linewidth: ， H1 and H2 are the total magnetic field strengths at the half-power point, which include the static magnetic field strength generated by the electromagnet measured in step 4 and the static magnetic field strength generated by the Helmholtz coil.

8. The measurement method as described in claim 7, characterized in that, The formula for calculating the half-power point transmission factor S21half is as follows: ， Wherein, S210 is the peak value of S21 measured after loading the sample in step 3, and S21c is the peak value of S21 measured at the ferromagnetic resonance point when loading the sample and energizing the electromagnet and Helmholtz coil in step 5.

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