Nonlinear excitation spin wave resonance linewidth test system and method based on vertical parametric pumping of microstrip lines

Abstract

The present invention provides a test system and method for measuring the linewidth of non-linear excited spin-wave resonance under vertical parametric pumping based on a microstrip line. The test system is as follows: A microwave source is connected to a power amplifier; the power amplifier is connected to one end of the microstrip line; a sample to be tested is placed on the microstrip line, and an external magnetic field is applied to the sample by an electromagnet, with the magnetic field direction perpendicular to the long axis direction of the microstrip line; the other end of the microstrip line is sequentially connected to a power attenuator, a detection diode, and a lock-in amplifier; and a computer terminal is connected. The test program is based on a LabVIEW control program, which regulates the magnetic field intensity of the electromagnet, real-time collects the amplitude of the output signal of the lock-in amplifier, and dynamically plots the voltage-magnetic field intensity relationship curve; when the microwave power is increased until the waveform undergoes non-linear distortion, the spin-wave resonance linewidth is calculated using a formula according to the critical microwave power and the threshold radio frequency magnetic field amplitude. Advantages: It realizes the measurement of the non-linear spin-wave resonance linewidth in an ultra-wide frequency band and with low power detection, improving the detection accuracy and operation efficiency.

Description

Technical Field

[0001] The present invention relates to the field of spin wave detection, and particularly to a method for testing the resonance linewidth of nonlinearly excited spin waves under vertical parametric pumping based on a microstrip line. Background Art

[0002] Microwave ferrite materials are materials with unique microwave magnetism. Due to their tensor permeability, Faraday rotation, and ferromagnetic resonance effects, they are widely used in various microwave ferrite devices, such as isolators, circulators, and phase shifters. In high-power ferrite devices, the spin wave resonance linewidth is used to measure the upper limit of the power carried by the material. When the microwave power exceeds a certain value, there will be power coupling between the coherent precession mode and the spin wave or direct coupling of the microwave magnetic field to the spin wave. At this time, the spin wave is parametrically excited, and its amplitude begins to grow unstably, and then the anomalous absorption of the microwave power by the material can be observed. The amplitude of the microwave magnetic field corresponding to the upper limit power is called the critical radio frequency magnetic field value, and the corresponding spin wave resonance linewidth can be obtained through calculation. Therefore, it is necessary and of great significance to measure the spin wave resonance linewidth of microwave ferrite materials, which directly measures the high-power performance of microwave ferrite materials. Therefore, it is meaningful to construct a test method for the resonance linewidth of nonlinearly excited spin waves.

[0003] At present, the test methods for the spin wave resonance linewidth of microwave ferrite materials in China are relatively single. The national standard GB / T 9633-2012 discloses a method for testing nonlinearly excited spin waves using a rectangular waveguide resonator under parallel parametric pumping. The so-called parallel parametric pumping means that the radio frequency magnetic field is parallel to the external magnetic field direction. However, most microwave ferrite devices operate in a state where the microwave radio frequency magnetic field is perpendicular to the external magnetic field. Therefore, the spin wave resonance linewidth measured under vertical parametric pumping can better characterize the high-power performance of the material in actual application. In addition, the test method using a rectangular waveguide resonator requires a large volume of the resonator, so a high-power microwave source is needed (usually the radio frequency microwave power at the sample position needs to reach dozens of watts to several kilowatts), and the parallel pumping method image also faces the problem of difficult to distinguish the starting point of distortion, and the test frequency is limited by the frequency of the resonator, and only single-frequency point testing can be achieved. Summary of the Invention

[0004] Based on the above problems, the present invention proposes a method and system for testing the resonance linewidth of nonlinearly excited spin waves under vertical parametric pumping based on a microstrip line. This method has a wide test frequency band, requires a small microwave power, has high test accuracy, and low cost.

[0005] Technical solution of the present invention: A method for testing the resonance linewidth of non-linearly excited spin waves under vertical parametric pumping based on a microstrip line. The components of the testing method are as follows: The microwave source is connected to the power amplifier, and the power amplifier is connected to one end of the microstrip line; The sample to be tested is placed on the microstrip line, and an external magnetic field is applied to the sample through an electromagnet. The direction of the magnetic field is perpendicular to the long axis direction of the microstrip line. The other end of the microstrip line is sequentially connected to a power attenuator, a detection diode, and a lock-in amplifier. The lock-in amplifier is connected to a computer through the microstrip line;

[0006] Implementation steps: Perform automated testing, and execute the following operations through the LabVIEW control program:

[0007] (1) Adjust the voltage of the electromagnet in a linear scanning manner to adjust the external static magnetic field strength of the electromagnet;

[0008] (2) Real-time collect the voltage signal output by the lock-in amplifier;

[0009] (3) Dynamically draw the relationship curve of voltage - static magnetic field strength;

[0010] Determine the non-linear excitation threshold: Gradually increase the output power of the microwave source. When a secondary resonance peak appears in the voltage - static magnetic field strength relationship curve when the external static magnetic field is lower than the ferromagnetic resonance field, record the current critical microwave power value , and calculate according to the following formula The corresponding critical radio frequency magnetic field amplitude ;

[0011] , where is the critical radio frequency magnetic field amplitude, with the unit of A / m, is the width of the microstrip line, with the unit of m, is the characteristic impedance of the microstrip line, with the unit of ohm, is the critical microwave power value measured by the LabVIEW control program, with the unit of watt;

[0012] Calculate the spin wave resonance linewidth : Calculate the spin wave resonance linewidth of the sample based on the formula , where, is the intrinsic ferromagnetic resonance angular frequency, , is the gyromagnetic ratio of the material, is the vacuum permeability, is the saturation magnetization intensity, is the microwave angular frequency, is the angle between the spin wave vector and the static magnetic field.

[0013] Further, the power amplifier is connected to a power meter, and the microwave power value incident on the microstrip line is monitored in real time through the power meter.

[0014] Preferably, the characteristic impedance of the microstrip line is measured by a vector network analyzer.

[0015] Preferably, the width of the microstrip line is measured by a vernier caliper.

[0016] Preferably, the test range of the spin-wave resonance linewidth is in the frequency band of 0.01 - 40 GHz.

[0017] A non-linear excitation spin-wave resonance linewidth test system based on the vertical parameter pumping of a microstrip line includes a microwave source, a power amplifier, a microstrip line, an electromagnet, a power attenuator, a detection diode, a lock-in amplifier, and a computer. The microwave source is connected to the power amplifier, the power amplifier is connected to one end of the microstrip line, the other end of the microstrip line is sequentially connected to the power attenuator, the detection diode, and the lock-in amplifier, the lock-in amplifier is connected to the computer through the microstrip line, the electromagnet is arranged on both sides of the microstrip line, a sample to be tested is placed on the microstrip line, an external magnetic field is applied to the sample by the electromagnet, the magnetic field direction is perpendicular to the long axis direction of the microstrip line, the computer contains a LabVIEW control program, the LabVIEW control program executes the steps of obtaining the voltage-static magnetic field intensity relationship curve, and is provided with an automatic calculation program. The automatic calculation program is provided with a data input table, and the data input table is used to input the width of the microstrip line, the characteristic impedance of the microstrip line, the gyromagnetic ratio of the material, the vacuum permeability, the saturation magnetization intensity, the microwave angular frequency, the included angle between the spin-wave wave vector and the static magnetic field. The automatic calculation program automatically identifies the voltage-static magnetic field intensity relationship curve, the power meter is connected to the computer, the automatic calculation program real-time collects the power value of the power meter, the automatic calculation program identifies the secondary resonance peak of the voltage-static magnetic field intensity relationship curve. When the secondary resonance peak appears, the power value of the power meter is the critical microwave power value, and the automatic calculation program calculates the spin-wave resonance linewidth according to the foregoing calculation formula of the spin-wave resonance linewidth.

[0018] The principle of the present invention: When a ferromagnetic sample is in a state where the microwave radio frequency magnetic field direction is perpendicular to the external magnetic field direction, the microwave photon with a frequency of and a wave vector will generate coherent precession magnons with the same frequency through a linear excitation process. At this time, these coherent precession magnons will decay into two magnon pairs with the same wave vector magnitude but opposite directions, and a frequency to satisfy the energy conservation and momentum conservation of the whole process. For a magnon with a wave number of k, its amplitude will be affected by the damping effect inside the ferrite material, resulting in the amplitude decaying with time. The amplitude decays to 1 / eThe time required for the multiplication is called the relaxation time of magnons or the relaxation time of spin waves. When the microwave radio frequency magnetic field is less than the critical radio frequency magnetic field value, the generation rate of magnons is less than the relaxation rate, and at this time, no observable amount of magnons can be detected. When the microwave power is high enough so that the microwave radio frequency magnetic field is greater than the critical radio frequency magnetic field value, the generation rate of magnons is greater than the relaxation rate, and the number of magnons is observable. At this time, the spin waves start to be nonlinearly excited, and their amplitude grows unstably. At this time, the anomalous absorption of the microwave power by the ferrite sample can be observed, which is reflected in the increase in loss when the external magnetic field is lower than the ferromagnetic resonance field, that is, the appearance of the sub-resonance peak. The microstrip line has the characteristic that the narrower the width, the larger the amplitude of the radio frequency magnetic field generated under the same microwave power. Therefore, compared with other methods, the required microwave power can be made smaller. By combining a lock-in amplifier to find the critical power for the generation of the sub-resonance, the resonance linewidth of the spin waves excited nonlinearly in the microwave ferrite material can be obtained.

[0019] Advantages of the present invention: (1) The present invention realizes the measurement of the resonance linewidth of spin waves in the ultra-wide frequency band of 0.01 - 20 GHz. By using a microwave source and a power amplifier with higher frequencies, the frequency band can be further broadened to 40 GHz.

[0020] (2) The present invention measures the resonance linewidth of spin waves to achieve non-linear spin wave excitation at a lower power. The required critical power is only at the level of a few hundred mW. The microwave power is small, no high-power microwave source is required, the energy consumption is low, the test cost is reduced, and the test steps are relatively simple, making the test more convenient and fast.

[0021] (3) The present invention measures the resonance linewidth of spin waves under vertical parametric pumping. At this time, the microwave radio frequency magnetic field is perpendicular to the direction of the external magnetic field. Therefore, it is closer to the actual situation when the device is in use. The resonance linewidth of the spin waves measured at this time can better characterize the performance of such devices at high powers.

[0022] (4) The judgment of whether the spectrogram of the resonance linewidth of spin waves measured by the present invention is distorted is clearer and more definite. When the sub-resonance occurs, it indicates that the spectrogram is distorted.

[0023] (5) The present invention has higher test accuracy. The present invention uses a lock-in amplifier for signal extraction. The lock-in amplifier can accurately extract weak signals in a strong noise background. Therefore, it can accurately detect the critical microwave power when the spectrogram is distorted. Description of the Drawings

[0024] Figure 1 It is a schematic diagram of the relative position relationship between the microstrip line, the sample and the electromagnet during the test;

[0025] Figure 2 It is a block diagram of the composition of each part of the test system;

[0026] Figure 3Microwave power absorption spectrum measured at a power of 200 mW as a function of magnetic field;

[0027] Figure 4 Microwave power absorption spectrum measured at a critical power of 443 mW as a function of magnetic field;

[0028] Figure 5 Microwave power absorption spectrum measured at a power exceeding the critical power of 600 mW as a function of magnetic field. Detailed implementation mode

[0029] The present invention mainly uses a microstrip line to generate a microwave radio frequency magnetic field, and detects the absorption intensity of the ferrite material for microwave power under different applied magnetic fields through a detection diode and a lock-in amplifier. The voltage source voltage signal of the electromagnet and the signal of the lock-in amplifier are read and collected by combining the LabVIEW control program in the computer, plotted after data processing, and then the microwave source power is adjusted to find the critical power value for generating sub-resonance absorption, and further the spin-wave resonance linewidth of the microwave ferrite is obtained.

[0030] The test system consists of: a microwave source, a power amplifier, a microstrip line, an electromagnet, a power attenuator, a detection diode, a lock-in amplifier, and a computer. The microwave source is connected to the power amplifier, the power amplifier is connected to one end of the microstrip line, and the other end of the microstrip line is successively connected to the power attenuator, the detection diode, and the lock-in amplifier. The lock-in amplifier is connected to the microstrip line and accesses the computer. The electromagnet is arranged on both sides of the microstrip line (as Figure 1 shown), and the sample to be tested is placed on the microstrip line. An external magnetic field is applied to the sample through the electromagnet, and the magnetic field direction is perpendicular to the long axis direction of the microstrip line. The microwave signal passes through the sample to be tested and then enters the power attenuator and the detection diode successively, and finally is connected to the lock-in amplifier. The entire test system is as Figure 2 shown.

[0031] (1) Connect a power meter to the power amplifier to read the microwave power after passing through the power amplifier. Place the sample on the microstrip line and at the center of the electromagnet yoke. The magnitude of the electromagnet magnetic field is determined by controlling the voltage of the voltage source by the computer LabVIEW control program.

[0032] (2) Control the voltage of the voltage source by the computer LabVIEW control program and read its value. After conversion by the formula (formula) ( , H is the voltage corresponding to the magnetic field, with the unit of Oe, U is the voltage of the voltage source, with the unit of V), the corresponding magnetic field value is obtained and used as the image x axis data, and the output signal value of the lock-in amplifier at the corresponding voltage is read as the image yAxis data is obtained to draw a voltage-static magnetic field intensity relationship curve. Since the microwave absorption amplitude of the ferrite sample varies under different magnetic fields, this curve can be regarded as the ferromagnetic resonance spectrum of the ferrite sample at the same microwave frequency and different external magnetic fields, with the maximum absorption amplitude at the resonance field.

[0033] (3) Adjust the output power of the microwave source and repeat the above test of the curve until the curve distortion phenomenon is just observed. Record the power value on the power meter as the critical microwave power. , and then calculate the amplitude of the threshold radio frequency magnetic field at the sample on the microstrip line. , and then through the spin wave resonance linewidth of the sample is obtained.

[0034] It should be noted that in step (1), the microstrip line together with the ferrite sample is placed in the middle of the electromagnet yoke, and the effect that the radio frequency microwave magnetic field is perpendicular to the magnetic field generated by the electromagnet should be achieved to correspond to the vertical parameter pumping situation of the spin wave non-linear excitation. In this case, the microwave energy is coupled with the coherent precession mode, that is, the ferromagnetic resonance mode, and the coherent precession mode is coupled with the spin wave mode again. When the microwave power exceeds the critical power, the spin wave begins to produce abnormal absorption, and its amplitude increases unstably, and the sub-resonance phenomenon can be observed.

[0035] In step (2), the signal of the lock-in amplifier picked up by the LabVIEW control program is absorbed by the sample, and the ferrite sample shows different absorption amplitudes under the action of the same frequency microwave for different external magnetic fields. Therefore, the signal in the lock-in amplifier can reflect the absorption degree of the sample under different external magnetic fields, and the spectrum obtained can represent the relationship between the microwave power loss and the external magnetic field magnitude.

[0036] The curve distortion phenomenon mentioned in step (3) refers to that in front of the resonance peak in the curve, a small sub-resonance peak appears when the external magnetic field is less than the resonance field.

[0037] Measurement example:

[0038] Connect the system, run the LabVIEW control program, control the voltage signal of the voltage source of the electromagnet, and read the voltage signal of the lock-in amplifier. Make a voltage-static magnetic field intensity relationship curve according to step (1), observe the reading of the power meter at this time, and record the microwave power absorption spectrum when the microwave power is 200 mW at this time, as Figure 3 shown.

[0039] According to step (2), find the spectrum where the waveform just starts to distort, that is, the sub-resonance phenomenon occurs, and its corresponding critical microwave power value, which is 443 mW here. The microwave power absorption spectrum at the critical microwave power is as Figure 4 shown. For comparison, the absorption spectrum image when the power exceeds the critical microwave power is tested, asFigure 5 As shown, the microwave power is 600 mW at this time.

[0040] Pre-measure the characteristic impedance and width of the microstrip line. Use a vector network analyzer to measure the characteristic impedance of the microstrip line used in the test to be 50 ohms, and then use a vernier caliper to measure the width of the microstrip line to be 0.5 mm. Use the formula to calculate the amplitude of the radio frequency magnetic field generated by the microstrip line when the critical microwave power value is 443 mW, that is, the critical radio frequency magnetic field amplitude. In the formula, is the critical radio frequency magnetic field amplitude, with the unit of A / m, is the width of the microstrip line, with the unit of m, is the characteristic impedance of the microstrip line, with the unit of ohm, is the critical microwave power value measured in the experiment, with the unit of watt. Substitute the experimental data to get .

[0041] Substitute into the conversion formula between the spin-wave resonance linewidth and the critical radio frequency magnetic field under vertical parametric pumping: , where in the formula is the spin-wave resonance linewidth, , is the gyromagnetic ratio of the measured material, 28 GHz / T, is the vacuum permeability , is the saturation magnetization of the material, 1800 G, is the microwave angular frequency used in the experiment, 5 GHz, is the direction of the spin-wave wave vector inside the ferrite. At the critical radio frequency magnetic field, it corresponds to 45°. Then, the spin-wave resonance linewidth of this material is 1.19 Oe at this time.

[0042] To improve the automation of calculations, in addition to containing the LabVIEW control program, the computer also has an automatic calculation program. The LabVIEW control program executes the steps to obtain the voltage-static magnetic field strength relationship curve in step (2). The automatic calculation program has a data input table, which is used to input the width of the microstrip line, the characteristic impedance of the microstrip line, the gyromagnetic ratio of the material, the vacuum permeability, the saturation magnetization, the microwave angular frequency, the angle between the spin-wave wave vector and the static magnetic field. The automatic calculation program automatically identifies the voltage-static magnetic field strength relationship curve. The power meter is connected to the computer. The automatic calculation program real-time collects the power value of the power meter. The automatic calculation program identifies the secondary resonance peak of the voltage-static magnetic field strength relationship curve. When the secondary resonance peak appears, the power value of the power meter is the critical microwave power value. The automatic calculation program automatically calculates the spin-wave resonance linewidth according to the above spin-wave resonance linewidth calculation formula. In this way, the time of manual observation can be reduced and missed detections can be avoided.

Claims

1. A method for testing the linewidth of non - linear excited spin - wave resonance under vertical parametric pumping based on microstrip lines, characterized in that, The components used in the test method are as follows: The microwave source is connected to the power amplifier, and the power amplifier is connected to one end of the microstrip line. The sample to be tested is placed on the microstrip line, and an external magnetic field is applied to the sample by an electromagnet. The direction of the magnetic field is perpendicular to the long axis direction of the microstrip line. The other end of the microstrip line is sequentially connected to a power attenuator, a detection diode, and a lock-in amplifier. The lock-in amplifier is connected to the microstrip line and accesses the computer. Implementation steps: Perform an automated test and execute the following operations through the LabVIEW control program: (1) Adjust the voltage of the electromagnet in a linear scanning manner to adjust the external static magnetic field strength of the electromagnet. (2) Collect the voltage signal output by the lock-in amplifier in real time. (3) Dynamically plot the relationship curve between voltage and static magnetic field strength. Determine the non-linear excitation threshold: Gradually increase the output power of the microwave source. When a secondary resonance peak appears in the voltage-static magnetic field intensity relationship curve when the externally applied static magnetic field is lower than the ferromagnetic resonance field, record the current critical microwave power value , and calculate the corresponding critical radio frequency magnetic field amplitude according to the following formula ; ; , where is the threshold radio frequency magnetic field amplitude, with the unit of A / m, is the microstrip line width, with the unit of m, is the characteristic impedance of the microstrip line, with the unit of ohm, is the critical microwave power value measured by the LabVIEW control program, with the unit of watt; Calculating the spin-wave resonance linewidth : Based on the formula calculate the spin-wave resonance linewidth of the sample, where is the eigen ferromagnetic resonance angular frequency, , is the gyromagnetic ratio of the material, is the permeability of free space, is the saturation magnetization, is the microwave angular frequency, is the angle between the spin-wave wave vector and the static magnetic field.

2. The method for testing the linewidth of non-linear excited spin wave resonance under vertical parametric pumping based on a microstrip line according to claim 1, wherein: The power amplifier is connected to a power meter, and the microwave power value incident on the microstrip line is monitored in real time through the power meter.

3. The method for testing the linewidth of non-linear excited spin wave resonance under vertical parametric pumping based on microstrip lines according to claim 1, wherein: The characteristic impedance of the microstrip line is measured using a vector network analyzer.

4. The method for testing the linewidth of non-linear excited spin wave resonance under vertical parametric pumping based on a microstrip line according to claim 1, wherein: The width of the microstrip line is measured using a vernier caliper.

5. The method for testing the linewidth of non - linear excited spin - wave resonance under vertical parametric pumping based on microstrip lines according to claim 1, characterized in that: The test range of the spin-wave resonance linewidth is in the frequency band range of 0.01 - 40 GHz.

6. A test system for the linewidth of non-linear excited spin wave resonance under vertical parametric pumping based on a microstrip line, comprising a microwave source, a power amplifier, a microstrip line, an electromagnet, a power attenuator, a detection diode, a lock-in amplifier, and a computer. The microwave source is connected to the power amplifier, the power amplifier is connected to one end of the microstrip line, the other end of the microstrip line is sequentially connected to the power attenuator, the detection diode, and the lock-in amplifier, and the lock-in amplifier is connected to the microstrip line and accessed to the computer, and is characterized in that: The electromagnets are arranged on both sides of the microstrip line. The sample to be tested is placed on the microstrip line, and an external magnetic field is applied to the sample by the electromagnets. The direction of the magnetic field is perpendicular to the long axis direction of the microstrip line. The computer contains a LabVIEW control program. The LabVIEW control program executes the steps for obtaining the relationship curve between voltage and static magnetic field strength in claim 1 and is provided with an automatic calculation program. The automatic calculation program is provided with a data input table for inputting the width of the microstrip line, the characteristic impedance of the microstrip line, the gyromagnetic ratio of the material, the vacuum permeability, the saturation magnetization intensity, the microwave angular frequency, the angle between the spin-wave wave vector and the static magnetic field. The automatic calculation program automatically identifies the relationship curve between voltage and static magnetic field strength. The power meter is connected to the computer. The automatic calculation program collects the power value of the power meter in real time. The automatic calculation program identifies the secondary resonance peak of the relationship curve between voltage and static magnetic field strength. When the secondary resonance peak appears, the power value of the power meter is the critical microwave power value. The automatic calculation program calculates the spin-wave resonance linewidth according to the calculation formula of the spin-wave resonance linewidth in claim 1.

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