Magneto-acoustic isolator preparation and test method based on horizontal shear surface acoustic wave

Abstract

The invention provides a preparation and test method of a magnetoacoustic isolator based on horizontal shearing surface acoustic waves, which relates to the field of surface acoustic wave devices, and comprises the following steps: determining the type and tangential direction of a piezoelectric substrate and the propagation angle of the surface acoustic waves according to the type of the surface acoustic waves so as to determine the wave velocity of the surface acoustic waves; the design of a surface acoustic wave delay line is completed based on the wave velocity of the surface acoustic wave, and the type of the surface acoustic wave at least comprises a horizontal shear surface acoustic wave; manufacturing the designed surface acoustic wave delay line on the determined piezoelectric substrate; and integrating a magnetic element on the determined piezoelectric substrate to obtain the magnetoacoustic isolator. The invention realizes the preparation of the spin wave magnetoacoustic isolator capable of stably exciting the horizontal shear surface acoustic wave.

Description

Technical Field

[0001] The present invention relates to the technical field of surface acoustic wave devices, and particularly to a preparation and testing method for a magneto-acoustic isolator based on horizontally polarized shear surface acoustic waves. Background Art

[0002] Surface Acoustic Wave (SAW) is an elastic wave propagating along the solid surface, which has the characteristics of high frequency, low loss and easy integration, and is widely used in filters, sensors and communication devices. However, traditional SAW devices have reciprocity, that is, the propagation direction of the wave does not affect its transmission characteristics, which limits its application in non-reciprocal devices (such as isolators and circulators).

[0003] In order to achieve non-reciprocal propagation of microwaves, magnetic elements are often introduced. Similarly, in the structure of a surface acoustic wave delay line, the time-reversal symmetry of SAW can be broken through magneto-acoustic coupling to achieve non-reciprocal propagation.

[0004] Therefore, how to realize an isolator based on magneto-acoustic coupling has become an urgent technical problem to be solved. Summary of the Invention

[0005] The present invention provides a preparation and testing method for a magneto-acoustic isolator based on horizontally polarized shear surface acoustic waves, so as to solve the defect that it is difficult to realize an isolator based on magneto-acoustic coupling in the prior art, and realize a preparation method for a magneto-acoustic isolator based on horizontally polarized shear surface acoustic waves, which is used to stably prepare a magneto-acoustic isolation device based on horizontally polarized shear surface acoustic waves.

[0006] The present invention provides a preparation method for a magneto-acoustic isolator based on horizontally polarized shear surface acoustic waves, including: Determine the type and tangential direction of the piezoelectric substrate and the propagation angle of the surface acoustic wave according to the type of the surface acoustic wave, so as to determine the wave velocity of the surface acoustic wave, and complete the design of the surface acoustic wave delay line based on the wave velocity of the surface acoustic wave, wherein the type of the surface acoustic wave includes at least horizontally polarized shear surface acoustic waves; Fabricate the designed surface acoustic wave delay line on the determined piezoelectric substrate; Integrate the magnetic element on the determined piezoelectric substrate to obtain a magneto-acoustic isolator.

[0007] According to the preparation method for a magneto-acoustic isolator based on horizontally polarized shear surface acoustic waves provided by the present invention, when the piezoelectric substrate is a lithium niobate substrate, the tangential direction of the piezoelectric substrate is the X direction, and the propagation angle of the surface acoustic wave is between 0 and -20° with respect to the Y crystal direction of the piezoelectric substrate.

[0008] A method for preparing a magnetoacoustic isolator based on horizontally sheared surface acoustic waves according to the present invention, wherein the surface acoustic wave delay line includes interdigital electrodes, a bus bar for leading out the interdigital electrodes, and pads. The interdigital electrodes include a set of input interdigital electrodes and a set of output interdigital electrodes. The step of fabricating the designed surface acoustic wave delay line on a determined piezoelectric substrate specifically includes: Etching the interdigital electrodes using a first type of lithography process; Etching the bus bar and pads using a second type of lithography process; Wherein, the precision of the first type of lithography process is higher than that of the second type of lithography process.

[0009] A method for preparing a magnetoacoustic isolator based on horizontally sheared surface acoustic waves according to the present invention, the step of designing the surface acoustic wave delay line based on the wave velocity of the surface acoustic wave specifically includes: Determining the wavelength of the surface acoustic wave based on the target frequency and the wave velocity of the surface acoustic wave; Determining the period and width of the interdigital electrodes constituting the surface acoustic wave delay line based on the wavelength, and completing the design of the surface acoustic wave delay line.

[0010] A method for preparing a magnetoacoustic isolator based on horizontally sheared surface acoustic waves according to the present invention, the step of integrating a magnetic element onto a determined piezoelectric substrate specifically includes: Integrating the magnetic element onto the piezoelectric substrate by means of magnetron sputtering.

[0011] A method for preparing a magnetoacoustic isolator based on horizontally sheared surface acoustic waves according to the present invention, the step of integrating a magnetic element onto a determined piezoelectric substrate specifically includes: Integrating the magnetic element onto the piezoelectric substrate using the mechanical exfoliation method, wherein the magnetic element is made of a two-dimensional magnetic material.

[0012] The present invention provides a magnetoacoustic isolator based on horizontally sheared surface acoustic waves, including: A piezoelectric substrate, which includes a substrate and a piezoelectric material on the substrate; A surface acoustic wave delay line, including interdigital electrodes integrated on the piezoelectric material, and the interdigital electrodes include a set of input interdigital electrodes and a set of output interdigital electrodes; A magnetic material, integrated on the piezoelectric material and located between a set of input interdigital electrodes and a set of output interdigital electrodes.

[0013] For a magnetoacoustic isolator based on horizontally sheared surface acoustic waves according to the present invention, the substrate is a silicon carbide substrate, and the piezoelectric material is a lithium niobate thin film.

[0014] The present invention provides a method for testing a magneto-acoustic isolator based on horizontally sheared surface acoustic waves, including: A vector network analyzer excites surface acoustic waves at the interdigital electrodes at the input end of the magneto-acoustic isolator and receives the electromagnetic signals converted by the interdigital electrodes at the output end to obtain scattering parameters, wherein the magneto-acoustic isolator is prepared by the method for preparing a magneto-acoustic isolator based on horizontally sheared surface acoustic waves according to any one of claims 1-6; Convert the scattering parameters to the time domain, intercept the acoustic wave signals after a preset time delay and convert them to the frequency domain to obtain the frequency spectrum of the acoustic wave signals; Obtain acoustic wave signals under multiple magnetic fields, normalize and organize them to obtain three-dimensional data characterizing frequency, magnetic field and amplitude, and test the isolation performance of the magneto-acoustic isolator based on the three-dimensional data.

[0015] According to the method for testing a magneto-acoustic isolator based on horizontally sheared surface acoustic waves provided by the present invention, the step of testing the isolation performance of the magneto-acoustic isolator based on the three-dimensional data specifically includes: Under the same magnetic field, calculate the first difference data between the three-dimensional data of the forward transmission coefficient in the scattering parameters and the three-dimensional data of the reverse transmission coefficient in the scattering parameters; or Calculate the second difference data between the three-dimensional data of the forward transmission coefficient in the scattering parameters under the sequential magnetic field and the three-dimensional data of the forward transmission coefficient in the scattering parameters under the reverse magnetic field; or Calculate the third difference data between the three-dimensional data of the reverse transmission coefficient in the scattering parameters under the sequential magnetic field and the three-dimensional data of the reverse transmission coefficient in the scattering parameters under the reverse magnetic field; Determine the isolation performance of the magneto-acoustic isolator based on the first difference data, the second difference data or the third difference data.

[0016] The method for preparing and testing a magneto-acoustic isolator based on horizontally sheared surface acoustic waves provided by the present invention determines the tangential direction of the piezoelectric substrate and the propagation angle of the surface acoustic wave according to the type of the surface acoustic wave to be excited, thereby simulating the wave velocity of the surface acoustic wave to be excited, and then realizing the design of the surface acoustic wave delay line based on the wave velocity, and preparing a magneto-acoustic isolator according to the designed surface acoustic wave delay line, so that the manufactured magneto-acoustic isolator can stably excite horizontally sheared surface acoustic waves to achieve a better isolation effect. Description of the Drawings

[0017] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0018] Figure 1 is a schematic flow chart of a method for fabricating a magneto-acoustic isolator based on horizontally sheared surface acoustic waves provided by the present invention; Figure 2 is a schematic structural diagram of a magneto-acoustic isolator fabricated by the method for fabricating a magneto-acoustic isolator based on horizontally sheared surface acoustic waves provided by the present invention; Figure 3 is one of the schematic diagrams of simulation results of the propagation angle in the method for fabricating a magneto-acoustic isolator based on horizontally sheared surface acoustic waves provided by the present invention; Figure 4 is the second of the schematic diagrams of simulation results of the propagation angle in the method for fabricating a magneto-acoustic isolator based on horizontally sheared surface acoustic waves provided by the present invention; Figure 5 is a schematic flow chart of a method for testing a magneto-acoustic isolator based on horizontally sheared surface acoustic waves provided by the present invention; Figure 6 is a test circuit diagram of the method for testing a magneto-acoustic isolator based on horizontally sheared surface acoustic waves provided by the present invention; Figure 7 is a flow chart for extracting acoustic wave signals in the method for testing a magneto-acoustic isolator based on horizontally sheared surface acoustic waves provided by the present invention; Figure 8 is a three-dimensional data diagram of S parameters obtained in the method for testing a magneto-acoustic isolator based on horizontally sheared surface acoustic waves provided by the present invention; Figure 9 is one of the schematic diagrams for characterizing the isolation performance in the method for testing a magneto-acoustic isolator based on horizontally sheared surface acoustic waves provided by the present invention; Figure 10 is the second of the schematic diagrams for characterizing the isolation performance in the method for testing a magneto-acoustic isolator based on horizontally sheared surface acoustic waves provided by the present invention; Figure 11 is the third of the schematic diagrams for characterizing the isolation performance in the method for testing a magneto-acoustic isolator based on horizontally sheared surface acoustic waves provided by the present invention; Figure 12 is the fourth of the schematic diagrams for characterizing the isolation performance in the method for testing a magneto-acoustic isolator based on horizontally sheared surface acoustic waves provided by the present invention; Figure 13 is a schematic structural diagram of an SH-SAW isolator with an X-Cut LiNbO 3 / CrCl 3 structure fabricated by the method for fabricating a magneto-acoustic isolator based on horizontally sheared surface acoustic waves provided by the present invention; Figure 14 is an X-Cut LiNbO fabricated by the method for fabricating a magneto-acoustic isolator based on horizontally sheared surface acoustic waves provided by the present invention 3 / CrCl3 Schematic diagram of test results of SH-SAW isolator with Figure 15 structure; it is an SH-SAW isolator with an X-Cut LiNbO 3 / CoFeB / Pt structure prepared by the method for preparing a magneto-acoustic isolator based on horizontally polarized surface acoustic wave provided by the present invention; Figure 16 it is an SH-SAW isolator with an X-Cut LiNbO 3 / FeGaB / MgO / FeGaB structure prepared by the method for preparing a magneto-acoustic isolator based on horizontally polarized surface acoustic wave provided by the present invention. Detailed implementation manners

[0019] To make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions in the present invention will be clearly and completely described below with reference to the accompanying drawings in the present invention. Apparently, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present invention without making creative efforts shall fall within the protection scope of the present invention.

[0020] First, the following content will be introduced: The main ways to achieve non-reciprocal propagation of surface acoustic waves include the following two: One is the chiral mismatch effect: through magneto-elastic coupling, the Rayleigh wave in the SAW forms an elliptically polarized driving magnetic field in the ferromagnet. When its chirality matches the magnetization precession direction of the ferromagnetic film, the energy conversion efficiency is relatively high; otherwise, it is suppressed.

[0021] The other is non-reciprocal spin wave dispersion: by means of the interface Dzyaloshinskii-Moriya (spin anti-symmetric exchange between neighboring magnetic moments) interaction or the interlayer dipole interaction, the symmetry of the spin wave dispersion is broken, and thus non-reciprocal propagation of the SAW is achieved.

[0022] When constructing a magneto-acoustic non-reciprocal device for isolating microwave signals based on the above principles, it is usually achieved by exciting Rayleigh waves.

[0023] Specifically, surface acoustic waves are elastic waves propagating along the solid surface, and there are various types, such as Rayleigh waves, SH-SAW (horizontally polarized surface acoustic waves), Sezawa waves, Leaky SAW (leaky surface acoustic waves), LLSAW (longitudinal leaky surface acoustic waves), etc. Among them, Rayleigh waves and SH-SAW are the most studied and used.

[0024] Rayleigh waves have two vibration components: a vertical shear wave component perpendicular to the surface of the piezoelectric medium and a longitudinal wave along the propagation direction. There is a 90° phase difference between the two, making Rayleigh waves elliptically polarized waves, and their energy is mainly concentrated within about one wavelength range on the medium surface; while the vibration direction of SH-SAW is parallel to the surface of the piezoelectric medium and perpendicular to the propagation direction, so it is called a horizontal shear wave.

[0025] At an appropriate propagation angle, compared with Rayleigh wave-based ones, the electromechanical coupling coefficient of the SH-SAW mode is much larger than that of other SAW modes such as Rayleigh waves, making the performance of the magneto-acoustic isolator based on SH-SAW better than that of the magneto-acoustic isolator based on Rayleigh waves. Among them, the electromechanical coupling coefficient is an important physical parameter describing the energy conversion efficiency between acoustic energy and electrical energy of a surface acoustic wave resonator, and is also a key performance parameter determining SAW devices, which is related to the device structure and the piezoelectric material itself.

[0026] In addition, Rayleigh waves attenuate significantly in the thickness direction of the thin film, and the magneto-elastic coupling with the magnetic thin film is limited, restricting the coupling strength between acoustic waves and spin waves. While SH-SAW is relatively uniform and has less attenuation in the thickness direction of the magnetic thin film, so it has a stronger magneto-elastic coupling with the magnetic thin film, thus effectively improving the coupling strength.

[0027] Furthermore, as a transverse wave, the wave velocity of SH-SAW is greater than that of Rayleigh waves, and a higher operating frequency can be obtained.

[0028] In summary, the magneto-acoustic isolator based on SH-SAW has better performance than the magneto-acoustic isolator based on Rayleigh waves. However, due to the greater difficulty in exciting SH-SAW, generally, the magneto-acoustic isolator based on Rayleigh waves is still used.

[0029] Therefore, the present invention provides a method for manufacturing a magneto-acoustic isolator to stably excite SH-SAW and manufacture a magneto-acoustic isolator based on SH-SAW.

[0030] The following combines Figure 1 and Figure 2 to introduce the method for manufacturing a magneto-acoustic isolator based on horizontal shear surface acoustic waves of the present invention. As Figure 1 shown, it includes: Step 101, determine the type and tangential direction of the piezoelectric substrate and the propagation angle of the surface acoustic wave according to the type of the surface acoustic wave, so as to determine the wave velocity of the surface acoustic wave, and complete the design of the surface acoustic wave delay line based on the wave velocity of the surface acoustic wave, where the type of the surface acoustic wave includes at least horizontal shear surface acoustic waves; The tangential direction of the piezoelectric substrate and the propagation angle of the surface acoustic wave jointly determine the characteristics of the surface acoustic wave, including wave velocity, electromechanical coupling coefficient, temperature stability, mode purity, attenuation, etc.

[0031] Specifically, different tangential directions of the piezoelectric substrate will cause changes in wave velocity and electromechanical coupling coefficient due to crystal anisotropy, and the propagation angle further affects the wave velocity and mode purity. Therefore, by reasonably selecting the tangential direction and propagation angle, the performance of SAW devices, such as the frequency response of filters and the sensitivity of sensors, can be optimized, thereby achieving higher energy conversion efficiency and temperature stability.

[0032] Therefore, in the preparation of the device, it is first necessary to select an appropriate tangential direction and propagation angle according to the type of surface acoustic wave to be excited.

[0033] In this embodiment, the type of surface acoustic wave can be Rayleigh wave or SH-SAW.

[0034] Optionally, for Y-Cut LiNbO 3 (Y-cut lithium niobate) thin film, when the acoustic wave propagation direction is along the Z crystal direction, Rayleigh wave can be best excited, and a magneto-acoustic isolator based on Rayleigh wave can be prepared.

[0035] Optionally, for X-Cut LiNbO 3 (X-cut lithium niobate) thin film, when the acoustic wave propagation direction forms an angle of about -10° with the Y crystal direction, the electromechanical coupling coefficient of SH-SAW is the strongest, and acoustic waves of other modes are suppressed.

[0036] In a feasible embodiment, the type and tangential direction of the piezoelectric substrate can be determined first, for example, the type and tangential direction of an easily obtainable piezoelectric substrate, and then based on the selected type and tangential direction of the piezoelectric substrate, simulation is carried out to determine the propagation angle corresponding to the target acoustic wave type.

[0037] On this basis, based on the determined type and tangential direction of the piezoelectric substrate, the surface acoustic wave, and the determined propagation angle, the wave velocity of the selected surface acoustic wave can be determined through simulation . Thus, the design of the surface acoustic wave delay line can be completed based on the wave velocity, specifically including the spacing, width, and delay time of a group of input interdigital electrodes and a group of output interdigital electrodes that make up the surface acoustic wave delay line.

[0038] Step 102, fabricate the designed surface acoustic wave delay line on the determined piezoelectric substrate; After determining the design of the surface acoustic wave delay line, the target surface acoustic wave delay line can be prepared on the selected piezoelectric substrate by etching or other feasible methods.

[0039] Optionally, the photolithography process in this embodiment can be any process that can realize the surface acoustic wave delay line, such as double photolithography.

[0040] It should be noted that since the wavelength of sound waves is five orders of magnitude smaller than that of electromagnetic waves, the volume of the magneto-acoustic isolator is much smaller than that of common ferrite isolation devices. Therefore, in a specific embodiment, lithography methods with higher precision such as extreme ultraviolet lithography and electron beam lithography can be used to etch the surface acoustic wave delay line, so as to achieve a precise lithography process on a piezoelectric substrate with a smaller volume.

[0041] Step 103: Integrate the magnetic element onto the determined piezoelectric substrate to obtain a magneto-acoustic isolator.

[0042] After the surface acoustic wave delay line is fabricated, integrate the magnetic element onto the selected piezoelectric substrate, and the fabricated magneto-acoustic isolator can be obtained.

[0043] Optionally, the magnetic element can be a soft magnetic, hard magnetic, composite magnet, or antiferromagnetic material.

[0044] Optionally, the integration process of the magnetic element can be selected according to the material of the piezoelectric substrate.

[0045] Optionally, the required magnetic structure can be grown through thin film deposition technology.

[0046] In a feasible embodiment, the magneto-acoustic isolator prepared by the above method is as Figure 2 shown, including a piezoelectric substrate composed of a layer of substrate and the piezoelectric material thereon. The surface acoustic wave delay line includes interdigital electrodes. The interdigital electrodes include a group of input interdigital electrodes (interdigital electrode 1) and a group of output interdigital electrodes (interdigital electrode 2), and are respectively arranged at both ends of the length direction of the piezoelectric material. The magnetic element is integrated on the piezoelectric substrate between the input interdigital electrode and the output interdigital electrode to provide a necessary magnetic environment for magneto-acoustic coupling.

[0047] Optionally, after fabrication, the performance of the obtained magneto-acoustic isolator can also be tested to determine its isolation performance.

[0048] The present invention determines the tangential direction of the piezoelectric substrate and the propagation angle of the surface acoustic wave according to the type of the surface acoustic wave to be excited, thereby simulating the wave velocity of the surface acoustic wave to be excited, and then realizing the design of the surface acoustic wave delay line based on the wave velocity, and preparing a magneto-acoustic isolator according to the designed surface acoustic wave delay line, so that the fabricated magneto-acoustic isolator can stably excite the horizontally polarized shear surface acoustic wave to achieve a better isolation effect.

[0049] In the method for preparing a magneto-acoustic isolator based on horizontally polarized shear surface acoustic waves of the present invention, when the piezoelectric substrate is a lithium niobate substrate, the tangential direction of the piezoelectric substrate is the X direction, and the propagation angle of the surface acoustic wave is between 0 and -20° with respect to the Y crystal direction of the piezoelectric substrate.

[0050] Since the tangential selection of the piezoelectric material in common piezoelectric substrates is mostly the X direction, the piezoelectric substrate is determined in advance to be a lithium niobate substrate, and the tangential direction of the piezoelectric material of the piezoelectric substrate is the X direction. Then, the optimal surface acoustic wave propagation angle is determined based on the test of the piezoelectric substrate in the X direction. Among them, the X direction means that the normal line of the piezoelectric substrate (wafer) is along the crystal orientation X axis direction.

[0051] Optionally, in this embodiment, taking the X-cut lithium niobate thin film as an example, it is experimentally obtained that when the propagation angle of the surface acoustic wave forms an angle of [-20, 0] degrees with the Y crystal orientation of the piezoelectric substrate, the electromechanical coupling coefficient of SH-SAW is the strongest, while the acoustic waves of other modes are suppressed.

[0052] Preferably, the propagation angle in this embodiment is determined to be -11° with respect to the Y crystal orientation of the piezoelectric substrate. Specifically, as Figure 3 and Figure 4 shown, the experimental simulation data shows that when the propagation angle is -11° with respect to the Y crystal orientation of the piezoelectric substrate, the best electromechanical coupling effect is achieved.

[0053] Using the piezoelectric substrate made of the above X-cut lithium niobate thin film and using -11° as the determined propagation angle for simulation design, the designed magneto-acoustic isolator can stably excite horizontal shear surface acoustic waves, realizing a magneto-acoustic isolator based on SH-SAW.

[0054] In the method for preparing a magneto-acoustic isolator based on horizontal shear surface acoustic waves according to the present invention, the surface acoustic wave delay line includes interdigital electrodes and a bus bar and pads for leading out the interdigital electrodes. The interdigital electrodes include a set of input interdigital electrodes and a set of output interdigital electrodes. The step of lithographically printing the designed surface acoustic wave delay line on the determined piezoelectric substrate specifically includes: Etching the pair of interdigital electrodes using a first type of lithography process; Etching the bus bar and pads using a second type of lithography process; Among them, the accuracy of the first type of lithography process is higher than that of the second type of lithography process.

[0055] It can be understood that a lithography process with higher accuracy usually has higher costs, including production costs and / or time costs. The surface acoustic wave delay line includes interdigital electrodes, as well as a bus bar and pads (Pad) for leading out the interdigital electrodes. The interdigital electrodes include a set of input interdigital electrodes and a set of output interdigital electrodes.

[0056] Therefore, in this embodiment, the etching of the interdigital electrodes, bus bars, and pads is carried out in two steps, so as to use different photolithography methods for structures with different precisions. When etching the interdigital electrodes, the first type of photolithography process with higher lithography precision is used to achieve better lithography effects, so as to stably excite SH-SAW; when etching the corresponding bus bars and pads, the second type of photolithography process with slightly worse precision but stronger economy is selected to balance the device effects and production costs.

[0057] In a specific embodiment, the interdigital electrodes are etched using the following first type of photolithography process: Clean the piezoelectric substrate: Soak it successively in acetone, isopropyl alcohol, and deionized water and ultrasonicate each for a period of time. After taking it out, dry it with nitrogen, and then heat it on a hot plate to remove the water vapor. Spin-coat the photoresist and conductive layer: Select an appropriate photoresist thickness according to the thickness and width of the interdigital electrodes. Optionally, use a double-layer resist process to make the subsequent stripping easier. After determining the thickness, select an appropriate rotation speed to spin-coat the photoresist, such as PMMA (PolyMethyl Methacrylate), and perform pre-baking treatment to remove the excess solvent in the photoresist, improve the adhesion of the photoresist to the substrate, and flatten the surface of the photoresist. Electron beam exposure: In the first type of photolithography process, during electron beam exposure, appropriately reduce parameters such as the beam current and beam spot size to ensure that the resolution meets the requirements of the device size. Development: First, wash away the conductive layer with deionized water, and then prepare a developer, which can be MIBK (Methyl IsobutylKetone) and IPA (Isopropyl Alcohol) configured in a ratio of 1:3. Develop at a low temperature, and then place it in an IPA fixing solution at the same temperature for about one minute. Finally, dry it with nitrogen. Evaporate and strip the metal thin film: Evaporate a certain thickness of metal (such as gold, aluminum, etc.) according to requirements. After evaporation, put it into an acetone solution and perform ultrasonic treatment with low power to strip and remove the excess metal outside the interdigital electrodes.

[0058] Through the above steps, the interdigital electrodes can be obtained. On this basis, the following second type of photolithography process is used to etch the large-sized bus bars and pad metal layers to complete the second photolithography process: The sorting process of the second photolithography process is similar to that of the first photolithography process. However, when spin-coating photoresist and conductive adhesive, the thickness can be made thicker to improve the success rate of stripping. After pre-baking, when using electron beam exposure, the resolution requirement is not high, and parameters such as beam current and beam spot diameter can be appropriately increased to improve the exposure speed, followed by development and fixing. When evaporating metal, the thickness can be appropriately increased. Then, use acetone for low-power ultrasonic cleaning for more than ten seconds to remove the excess metal, and rinse with IPA to prevent metal debris from adhering to the interdigital electrodes and causing device failure. Finally, dry with nitrogen and observe whether the device structure is intact under a scanning electron microscope (SEM).

[0059] Generally speaking, in the second type of photolithography process in this embodiment, since the precision requirement is relatively low, the time required for the photolithography process is shorter.

[0060] In the present invention, different photolithography processes are selected for the interdigital electrodes, bus bars, and pads with different precision requirements, and the lithography of the interdigital electrodes, bus bars, and pads is carried out in two steps to complete the preparation of the surface acoustic wave delay line, so as to ensure that the prepared magnetoacoustic isolator can stably excite SH-SAW and the production cost is optimal.

[0061] In the method for preparing a magnetoacoustic isolator based on horizontally polarized surface acoustic waves of the present invention, the step of designing the surface acoustic wave delay line based on the wave velocity of the surface acoustic wave specifically includes: Determining the wavelength of the surface acoustic wave based on the target frequency and the wave velocity of the surface acoustic wave; Based on the wavelength, determining the period and width of the interdigital electrodes constituting the surface acoustic wave delay line, and completing the design of the surface acoustic wave delay line.

[0062] The surface acoustic wave delay line includes a set of input interdigital electrodes and a set of output interdigital electrodes, and its design process is mainly the design of parameters such as the period, width, and length of the input interdigital electrodes / output interdigital electrodes.

[0063] Specifically, after simulating and determining the wave velocity of the target surface acoustic wave the delay time of the surface acoustic wave delay line can be obtained from the wave velocity and the distance between the input interdigital electrodes and the output interdigital electrodes.

[0064] In addition, the wavelength of the target surface acoustic wave is determined according to the target frequency of the magnetoacoustic isolator to be prepared: ; Based on the wavelength, determining the period of the interdigital electrodes, that is, the distance between the input interdigital electrodes and the output interdigital electrodes: ; According to the period, determining the width of the input interdigital electrodes / output interdigital electrodes: .

[0065] Furthermore, according to the wavelength The thickness of the piezoelectric material on the substrate can also be determined. For example, for an LNOI substrate (Lithium Niobate on Insulator) with a 3 3 / SiO 2 / Si (lithium niobate / silicon dioxide / silicon) structure, where the thickness of LiNbO 3 is generally between 0.1 and 0.2 . Considering the compensation of sound velocity and temperature by SiO 2 , the thickness of SiO 2 can be determined to be about 0.2 .

[0066] In addition, the number of pairs and the length of the input interdigital electrodes / output interdigital electrodes also need to be designed. Among them, the larger the number of pairs, the smaller the insertion loss, but the narrower the bandwidth and the larger the capacitance, which is likely to cause the suppression of high-frequency signals; the larger the length of the interdigital electrodes, the smaller the diffraction loss and the more concentrated the acoustic wave energy, but the capacitance will also be larger. In addition, the type and thickness of the metal material used for the interdigital electrodes also affect the electromechanical coupling coefficient and the sound velocity.

[0067] After determining the above conditions, relevant simulation software such as COMSOL (a multi-physics field modeling and simulation software) is used for simulation according to requirements to obtain the optimal design, and finally the design scheme of the surface acoustic wave delay line based on the wave velocity is completed.

[0068] In the method for preparing a magneto-acoustic isolator based on horizontal shear surface acoustic waves according to the present invention, the step of integrating the magnetic element on the determined piezoelectric substrate specifically includes: Integrating the magnetic element on the piezoelectric substrate by means of magnetron sputtering.

[0069] Optionally, the integration of the magnetic element is similar to the lithography of the bus bar and the Pad metal, and the magnetic element is prepared based on magnetron sputtering.

[0070] In a specific embodiment, a layer of photoresist is spin-coated and pre-baked. Using low-resolution and fast electron beam exposure parameters, the pattern of the magnetic element part is lithographed on the surface acoustic wave delay line. After developing and fixing, the parameters such as the power of the radio frequency power supply, the ratio of argon to nitrogen, the air pressure, and the time are set, and the required magnetic structure is grown by magnetron sputtering, such as FeGaB / MgO / FeGaB (iron gallium boron / magnesium oxide / iron gallium boron), NiFe / Ru / NiFe (nickel iron / ruthenium / nickel iron), and Ti / CoFeB (titanium / iron cobalt boron), etc.; finally, it is soaked in acetone for stripping.

[0071] Optionally, if the stripping is difficult, it can be heated in a water bath at 80°C for about 10 minutes.

[0072] In the above - mentioned manner, after the surface acoustic wave delay line is fabricated, the integration of the magnetic element and the surface acoustic wave delay line can be achieved, and the fabrication of the magneto - acoustic isolator is completed.

[0073] In the method for fabricating a magneto - acoustic isolator based on horizontally - sheared surface acoustic waves according to the present invention, the step of integrating the magnetic element onto a determined piezoelectric substrate specifically includes: Integrating the magnetic element onto the piezoelectric substrate using the mechanical exfoliation method, wherein the magnetic element is made of a two - dimensional magnetic material.

[0074] Optionally, when the magnetic element uses two - dimensional magnetic materials such as CrI 3 、Fe 3 GeTe 2 、Cr 2 Ge 2 Te 6 (ferromagnetic chromium iodide, iron germanium telluride, chromium germanium telluride), etc., which are intrinsic two - dimensional magnetic materials, the integration of the magnetic element can also be achieved by the mechanical exfoliation method.

[0075] Specifically, by repeatedly peeling off the bulk single crystal with a tape, obtaining flakes in the range of dozens of nanometers to hundreds of nanometers, screening samples with appropriate shapes using an optical microscope, and then transferring the exfoliated samples onto the surface of the two - dimensional material.

[0076] In the above - mentioned manner, the fabrication of a magneto - acoustic isolator can be achieved, and the fabricated magneto - acoustic isolator can stably excite SH - SAW.

[0077] The following describes a magneto - acoustic isolator based on horizontally - sheared surface acoustic waves provided by the present invention. The magneto - acoustic isolator based on horizontally - sheared surface acoustic waves described below is fabricated according to the method for fabricating a magneto - acoustic isolator based on horizontally - sheared surface acoustic waves described above.

[0078] As Figure 2 shown, the magneto - acoustic isolator based on horizontally - sheared surface acoustic waves of the present invention includes a piezoelectric substrate, a surface acoustic wave delay line, and a magnetic material.

[0079] Among them, the piezoelectric substrate includes a substrate and a piezoelectric material on the substrate. Optionally, the substrate can be any silicon - based material, or sapphire, SiC, quartz, etc. Optionally, the piezoelectric material can be lithium niobate, lithium tantalate, aluminum nitride, etc. The substrate and the piezoelectric material together form the piezoelectric substrate.

[0080] The surface acoustic wave delay line includes interdigital electrodes. The interdigital electrodes include a set of input interdigital electrodes and a set of output interdigital electrodes. The distribution direction of the interdigital electrodes is determined according to the type of surface acoustic wave to be excited; the period and width of the interdigital electrodes are determined according to the target frequency of the magneto - acoustic isolator.

[0081] For example, when the surface acoustic wave to be excited is SH-SAW, the input interdigital electrode and the output interdigital electrode are distributed at about -11° with respect to the Y crystal orientation of the substrate to stably excite SH-SAW.

[0082] The magnetic material is integrated between the input interdigital electrode and the output interdigital electrode on the piezoelectric substrate. Optionally, the magnetic material can be a natural antiferromagnetic material such as CrCl 3 , or a ferromagnetic metal or a multi-layer film composed of a ferromagnetic metal and a heavy metal material, etc.

[0083] In the magneto-acoustic isolator based on the horizontally polarized shear surface acoustic wave of the present invention, the substrate is a silicon carbide substrate, and the piezoelectric material is a lithium niobate thin film.

[0084] As a preference, in this embodiment, the substrate is selected as SiC (silicon carbide) material, and the piezoelectric material is selected as X-CutLiNbO 3 , to obtain a substrate of LiNbO 3 / SiC structure as the piezoelectric substrate.

[0085] The selected LiNbO 3 / SiC piezoelectric substrate in this embodiment, compared with the common LiNbO 3 / SiO 2 / Si substrate, omits the SiO 2 buffer layer, has a simpler structure and fewer interface defects, which is beneficial to improving the film quality. Compared with Si, SiC has better mechanical strength and thermal conductivity. Further, the thermal expansion coefficients of SiC and LiNbO 3 are close, while the thermal expansion coefficient difference between LiNbO 3 and Si is large. Therefore, the LiNbO 3 / SiC piezoelectric substrate can significantly reduce the stress during temperature cycling, improve the temperature stability, and is more suitable for low-temperature environments.

[0086] Next, a test method for the magneto-acoustic isolator based on the horizontally polarized shear surface acoustic wave of the present invention will be described. The test method for the magneto-acoustic isolator based on the horizontally polarized shear surface acoustic wave described below is used to test the magneto-acoustic isolator prepared by any of the above-described preparation methods for the magneto-acoustic isolator based on the horizontally polarized shear surface acoustic wave.

[0087] As Figure 5 shown, the test method for the magneto-acoustic isolator based on the horizontally polarized shear surface acoustic wave of the present invention includes: Step 501, the vector network analyzer excites a surface acoustic wave at the interdigital electrode at the input end of the magneto-acoustic isolator and receives the electromagnetic signal converted by the interdigital electrode at the output end to obtain scattering parameters; Since some of the magnetoacoustic isolators to be prepared need to work in a small magnetic field environment, therefore, the test method of the magnetoacoustic isolator of the present invention uses a test platform integrated with a magnet. The test platform includes three main components: a probe station, a vector network analyzer (VNA), and a magnet. A computer program is used to control the magnet and the VNA to perform magnetic field regulation and the test and reading of scattering parameters (S parameters). The test circuit is as Figure 6 shown.

[0088] Specifically, before performing the S parameter test, the probe station is first calibrated using a calibration chip. During the test, the VNA emits a detection pulse with a nanosecond pulse width. The detection pulse is a microwave pulse. The microwave pulse excites surface acoustic waves on the interdigital electrodes at the input end of the magnetoacoustic isolator to be tested, and propagates through the piezoelectric substrate to the output end interdigital electrodes and is converted into an electromagnetic signal. The electromagnetic signal is received by the receiving end of the VNA and the S parameter is detected.

[0089] Step 502, convert the scattering parameter to the time domain, intercept the acoustic wave signal after a preset time delay and convert it to the frequency domain to obtain the frequency spectrum of the acoustic wave signal; In order to extract the surface acoustic wave signal, the detected S parameter needs to be inverse Fourier transformed to the time domain. As Figure 7 shown, in the time domain, it can be found that within a certain period of time at the beginning, there is a strong electromagnetic signal. This part of the energy does not propagate through the acoustic wave, but is an electromagnetic wave signal with a very fast speed (as Figure 7 shown by the yellow box in), and the real acoustic wave signal appears near the delay time (as Figure 7 shown by the green box in).

[0090] Therefore, when extracting the acoustic wave signal, this period of time is used as the preset time, and the acoustic wave signal after the preset time is intercepted. It is considered that the acoustic wave pulse at this time (as Figure 7 shown by the blue box in) is the acoustic wave signal to be extracted. It can be understood that the piezoelectric material and / or magnetic material of the magnetoacoustic isolator to be tested are different, and the preset time is different, but for the same type of magnetoacoustic isolator to be tested, the preset time is the same.

[0091] Optionally, in this embodiment, corresponding to the SH-SAW isolator with the X-Cut LiNbO 3 / CrCl 3 (chromium chloride) structure, the preset time is 60 nanoseconds.

[0092] The intercepted acoustic wave signal is Fourier transformed to the frequency domain to obtain the acoustic wave transmission characteristics of the prepared surface acoustic wave delay line.

[0093] Step 503, obtain the acoustic wave signals under multiple magnetic fields, normalize and organize them to obtain three-dimensional data characterizing frequency, magnetic field, and amplitude, and test the isolation performance of the magnetoacoustic isolator based on the three-dimensional data.

[0094] Further, a set of S-parameters was measured in the above-described manner under multiple magnetic fields of different magnitudes. Therefore, it is necessary to normalize the S-parameters measured under each magnetic field.

[0095] Optionally, the S-parameters measured under each magnetic field (linear scale, unit: 1) are divided by the S-parameters measured under the maximum magnetic field (linear scale, unit: 1), so as to obtain a three-dimensional data set, as Figure 8 shown. The horizontal axis represents the magnitude of the magnetic field, the vertical axis represents the frequency of the S-parameters, and the color at each coordinate represents the normalized S-parameter modulus at a specific magnetic field and frequency.

[0096] Based on this normalized S-parameter model, that is, the three-dimensional data representing frequency, magnetic field, and amplitude, the isolation performance of the magneto-acoustic isolator prepared can be measured by comparing the modulus of S21 (forward transmission coefficient) with the modulus of S12 (reverse transmission coefficient).

[0097] By intercepting the acoustic wave signal after a preset time delay, the present invention can more accurately extract the acoustic wave signal, so as to perform the performance test of the isolation function of the magneto-acoustic isolator based on the extracted acoustic wave signal.

[0098] In the method for testing a magneto-acoustic isolator based on horizontally polarized shear surface acoustic waves according to the present invention, the step of testing the isolation performance of the magneto-acoustic isolator based on the three-dimensional data specifically includes: Calculating a first difference data set between the three-dimensional data of the forward transmission coefficient in the scattering parameters and the three-dimensional data of the reverse transmission coefficient in the scattering parameters under the same magnetic field; Determining the isolation performance of the magneto-acoustic isolator based on the first difference data set.

[0099] In order to characterize the isolation performance, in one embodiment, the modulus of S21 can be compared with the modulus of S12 under the same magnetic field, that is, the three-dimensional data of S21 is subtracted from the three-dimensional data of S12, so as to clearly show the isolation performance of the magneto-acoustic isolator under different magnetic fields. Among them, the moduli used in the calculation are all transformed into logarithmic scale in dB after normalization.

[0100] In a specific embodiment, the three-dimensional data of S21 is subtracted from the three-dimensional data of S12, and the obtained first difference data set is as Figure 9 shown. A spectral line at a frequency of 2.5 GHz is intercepted from Figure 9 as Figure 10 shown. It can be seen that the isolation degree of the tested magneto-acoustic isolator is approximately about 0.1 dB.

[0101] Calculating second difference data between the three-dimensional data of the forward transmission coefficient in the scattering parameters under the sequential magnetic field and the three-dimensional data of the forward transmission coefficient in the scattering parameters under the reverse magnetic field; or Calculating third difference data between the three-dimensional data of the reverse transmission coefficient in the scattering parameters under the sequential magnetic field and the three-dimensional data of the reverse transmission coefficient in the scattering parameters under the reverse magnetic field; The isolation performance of the magneto-acoustic isolator is determined based on the second difference or the third difference.

[0102] When testing the S parameters, the magnetic field is swept from the negative field to the positive field. Since the non-reciprocity is directly related to the direction of the magnetic field, when characterizing the isolation performance, the three-dimensional data of S21 under the sequential magnetic field can be subtracted from the three-dimensional data of S21 under the reverse magnetic field to obtain the second difference data; or the three-dimensional data of S12 under the sequential magnetic field can be subtracted from the three-dimensional data of S21 under the reverse magnetic field to obtain the third difference data.

[0103] The second difference data or the third difference data can also be used to show the isolation performance of the magnetic acoustic isolator under different magnetic fields. In a feasible implementation, a second difference data such as Figure 11 As shown, from Figure 11 The spectrum line diagram at the intercept frequency of 2.49GHz is as follows Figure 12 As shown, it can be seen that the isolation degree of the tested magnetic-acoustic isolator is about 0.1dB.

[0104] On the basis of the above, in a specific embodiment, the X-Cut LiNbO 3 / CrCl 3 The SH-SAW isolator of the structure is used, and the isolation performance test is carried out using the magneto-acoustic isolator test method based on horizontal shear surface acoustic wave of the present invention, and the process and results are as follows: During the preparation process, a piece of X-Cut LiNbO 3 The substrate is cleaned according to the above steps, the photoresist is spin-coated and pre-baked, and then the conductive layer is spin-coated. Using an IDT delay line layout with a base frequency of about 2.5 GHz, the IDT is distributed at about -10° along the Y crystal direction of the substrate. After the substrate crystal direction and the layout are aligned, the electron beam exposure and evaporation are measured according to the above preparation method, and the interdigital electrodes, bus bars and Pad electrodes (Al (90 nm)) are peeled off respectively to complete the preparation of the surface acoustic wave delay line.

[0105] On the substrate of the existing IDT delay line, CrCl was separated by mechanical stripping. 3 Tear off a thickness of about 100 nanometers and then transfer it between two IDTs to obtain a complete device. Figure 13 shown.

[0106] For the magnetoacoustic isolator based on natural antiferromagnetic materials in this embodiment, the interlayer dipole interaction breaks the spatial symmetry of the dipole field, causing a non-reciprocal spin wave dispersion relation (such as Figure 14 As shown, the spin wave in this example is CrCl 3 The acoustic branch is used instead of the optical branch. The optical branch has weak absorption of sound waves and is not used), which causes non-reciprocal propagation of surface acoustic waves and realizes the isolation function.

[0107] Furthermore, the prepared X-Cut LiNbO 3 / CrCl 3 The magnetic acoustic isolator of the structure was tested, and the results are as follows Figure 14 As shown in the figure, when the magnetic field direction forms an angle of 0° or 90° with the SH-SAW propagation direction (with an error range of ±20°), and the magnetic field is fixed at around 500Oe, the propagation of the sound wave will show obvious non-reciprocity, achieving the isolation function of microwaves in the frequency band around 2.5GHz (about 0.1dB). When the magnetic field is added to the ferromagnetic resonance magnetic field corresponding to the third-order, fifth-order and other odd-order frequencies of the IDT, the isolation function can also be achieved. It is worth noting that due to the dominant magnetic anisotropy of antiferromagnetic materials under low magnetic fields, the isolation of the device will be stronger, for CrCl 3 Generally speaking, the smaller the magnetic field, the lower the acoustic antiferromagnetic resonance frequency, and it is expected that there will be an isolation of about 3dB at around 1.1GHz.

[0108] In another specific embodiment, the X-Cut LiNbO 3 / CoFeB / Pt (X-cut lithium niobate / cobalt iron boron / platinum) structure SH-SAW isolator, and the isolation performance test of the magneto-acoustic isolator based on horizontal shear surface acoustic wave of the present invention is carried out, and its process and results are as follows: During the preparation process, a piece of X-Cut LiNbO 3 The substrate is used as a piezoelectric substrate. The substrate is cleaned according to the above steps, a photoresist is spin-coated and pre-baked, and then a conductive layer is spin-coated; Using an IDT delay layout with a base frequency of about 1 GHz, the IDT is distributed at about -10° along the Y crystal direction of the substrate. After the substrate crystal direction and the layout are aligned, the interdigital electrodes, bus bars and Pad electrodes are peeled off according to the above preparation method (in order to improve the performance of the IDT at high frequencies, a layer of Ti is first plated, and the electrode structure is Ti (10nm) / Al (60nm)); On the substrate of the existing IDT delay line, an electron beam exposure is used to etch the area pattern of the magnetic thin film. After developing and fixing, a CoFeB(1.6nm) / Pt(3 nm) thin film is magnetron sputtered, and then peeled off to obtain a complete device, such as Figure 15 shown.

[0109] For the magnetoacoustic isolator prepared by this embodiment, by introducing heavy metals (such as Pt, Ta, etc.), there is a Dzyaloshinskii-Moriya interaction (DMI) at the interface between the ferromagnetic metal and the heavy metal, thus causing a non-reciprocal spin-wave dispersion relation, such as Figure 14 shown. When a microwave signal with a frequency of f1 is input into the device, the acoustic wave propagating forward (corresponding to +k) cannot be coupled with the spin wave and cannot be dissipated through the spin wave, so it can propagate to the other side IDT. The acoustic wave propagating backward (corresponding to -k) can be coupled with the spin wave and dissipated through the spin wave and cannot propagate to the other side IDT, thereby realizing the isolation function.

[0110] Furthermore, the prepared magnetoacoustic isolator is tested using the above test method. When the magnetic field direction and the SH-SAW propagation direction are 0° (within an error range of ±20°), and the magnetic field adjusts the ferromagnetic resonance frequency of the ferromagnetic material to odd frequencies such as the fundamental frequency, third-order frequency, and fifth-order frequency of the IDT, the propagation of the acoustic wave will exhibit obvious non-reciprocity, realizing the isolation function of microwaves in frequency bands near 1 GHz, 3 GHz, 5 GHz, etc.

[0111] In another specific embodiment, an SH-SAW isolator with an X-Cut LiNbO 3 / FeGaB / MgO / FeGaB structure is prepared by the method for preparing a magnetoacoustic isolator based on horizontally polarized shear acoustic surface waves of the present invention, and the isolation performance is tested using the test method for a magnetoacoustic isolator based on horizontally polarized shear acoustic surface waves of the present invention. The process and results are as follows: During the preparation process, a piece of X-Cut LiNbO 3 substrate is prepared as the piezoelectric substrate. The substrate is cleaned, photoresist is spin-coated and pre-baked according to the foregoing steps, and then a conductive layer is spin-coated; The layout of the IDT delay line with a fundamental frequency of about 300 MHz is used. Optionally, in order to improve the excitation effect of high odd harmonics, the interdigital electrodes are designed with split fingers. The IDT is distributed at an angle of about -10° with respect to the Y crystal direction of the substrate. After aligning the substrate crystal direction with the layout, according to the above preparation method, the interdigital electrodes, bus bars, and Pad electrodes (Al(70nm)) are peeled off respectively; On the substrate of the existing IDT delay line, an electron beam exposure is used to etch the regional pattern of the magnetic thin film. After development and fixation, an FeGaB(15nm) / MgO(4 nm) / FeGaB(15nm) thin film is magnetron sputtered, and then peeled off to obtain a complete device, such as Figure 16 shown. It should be noted that when growing such artificial antiferromagnetic thin films, an external magnetic field needs to be applied in the growth environment. When growing the top layer of FeGaB, the sample should be rotated 180°, and the direction of the external magnetic field remains unchanged, so that the magnetization of the top layer of FeGaB is reversed from that of the bottom layer of FeGaB. In this example, the direction of the external magnetic field forms a 90° angle with the direction of acoustic wave propagation.

[0112] For the magnetoacoustic isolator prepared in this embodiment, for the artificial antiferromagnetic structure, there is an interlayer dipole interaction, which breaks the spatial symmetry of the dipole field, thereby causing a non-reciprocal spin wave dispersion relation.

[0113] Furthermore, using the above test method to test the prepared magnetoacoustic isolator, when the magnetic field direction is perpendicular to the external magnetic field direction during magnetron sputtering (that is, when the magnetic field direction forms 0° and 90° angles with the SH-SAW propagation direction), and the magnetic field adjusts the ferromagnetic resonance frequency of the ferromagnetic material to odd frequencies such as the fundamental frequency, third-order frequency, and fifth-order frequency of the IDT, the propagation of the acoustic wave will show obvious non-reciprocity, realizing the isolation function of microwaves in frequency bands near 0.3 GHz, 0.9 GHz, 1.5 GHz, 2.1 GHz, etc.

[0114] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for preparing a magnetoacoustic isolator based on horizontal shear surface acoustic wave, characterized in that: include: Determining the type and tangent direction of the piezoelectric substrate and the propagation angle of the surface acoustic wave according to the type of the surface acoustic wave, thereby determining the wave velocity of the surface acoustic wave, and completing the design of the surface acoustic wave delay line based on the wave velocity of the surface acoustic wave, wherein the type of the surface acoustic wave at least includes a horizontal shear surface acoustic wave; The designed surface acoustic wave delay line is fabricated on a certain piezoelectric substrate; The magnetic element is integrated into a certain piezoelectric substrate to obtain a magnetoacoustic isolator.

2. The method for preparing a magnetoacoustic isolator based on horizontal shear surface acoustic wave according to claim 1, characterized in that: In the case where the piezoelectric substrate is a lithium niobate substrate, the tangential direction of the piezoelectric substrate is the X direction, and the propagation angle of the surface acoustic wave is between 0 and -20° with respect to the Y crystal direction of the piezoelectric substrate.

3. The method for preparing a magnetoacoustic isolator based on horizontal shear surface acoustic wave according to claim 1, characterized in that: The surface acoustic wave delay line comprises interdigital electrodes and bus bars and pads for leading out the interdigital electrodes, the interdigital electrodes comprise a group of input interdigital electrodes and a group of output interdigital electrodes, and the step of fabricating the designed surface acoustic wave delay line on a determined piezoelectric substrate specifically comprises: Etching the interdigitated electrodes using a first type of photolithography process; Using a second type of photolithography process to etch and obtain the bus bar and the pad; Among them, the precision of the first type of photolithography process is higher than that of the second type of photolithography process.

4. The method for preparing a magnetoacoustic isolator based on horizontal shear surface acoustic wave according to claim 1, characterized in that: The step of completing the design of the surface acoustic wave delay line based on the wave velocity of the surface acoustic wave specifically includes: determining a wavelength of the surface acoustic wave based on the target frequency and the wave velocity of the surface acoustic wave; The period and width of the interdigital electrodes constituting the surface acoustic wave delay line are determined based on the wavelength, thereby completing the design of the surface acoustic wave delay line.

5. The method for preparing a magnetoacoustic isolator based on horizontal shear surface acoustic wave according to claim 1, characterized in that: The step of integrating the magnetic element into the determined piezoelectric substrate specifically includes: The magnetic element is integrated on the piezoelectric substrate by magnetron sputtering.

6. The method for preparing a magnetoacoustic isolator based on horizontal shear surface acoustic wave according to claim 1, characterized in that: The step of integrating the magnetic element into the determined piezoelectric substrate specifically includes: A magnetic element is integrated into the piezoelectric substrate by using a mechanical peeling method, wherein the magnetic element is made of a two-dimensional magnetic material.

7. A magneto-acoustic isolator based on horizontal shear surface acoustic wave, characterized in that: The method for preparing a magnetic acoustic isolator based on horizontal shear surface acoustic wave according to any one of claims 1 to 6 comprises: A piezoelectric substrate, the piezoelectric substrate comprising a substrate and a piezoelectric material on the substrate; A surface acoustic wave delay line, comprising interdigital electrodes integrated on a piezoelectric material, wherein the interdigital electrodes include a group of input interdigital electrodes and a group of output interdigital electrodes; The magnetic material is integrated on the piezoelectric material and is located between the input interdigital electrodes and the output interdigital electrodes.

8. The magneto-acoustic isolator based on horizontal shear surface acoustic wave according to claim 7, characterized in that: The substrate is a silicon carbide substrate, and the piezoelectric material is a lithium niobate film.

9. A method for testing a magnetoacoustic isolator based on horizontal shear surface acoustic waves, characterized in that: include: The vector network analyzer excites surface acoustic waves at the interdigital electrodes at the input end of the magnetoacoustic isolator, and receives electromagnetic signals converted by the interdigital electrodes at the output end to obtain scattering parameters, wherein the magnetoacoustic isolator is prepared by the method for preparing a magnetoacoustic isolator based on horizontal shear surface acoustic waves as described in any one of claims 1 to 6; The scattering parameters are converted into the time domain, and the sound wave signal is intercepted after a delay of a preset time length and converted into the frequency domain to obtain the spectrum of the sound wave signal; Acoustic wave signals under multiple magnetic fields are acquired, normalized and sorted to obtain three-dimensional data representing frequency, magnetic field and amplitude, and the isolation performance of the magneto-acoustic isolator is tested based on the three-dimensional data.

10. The method for testing a magneto-acoustic isolator based on horizontal shear surface acoustic waves according to claim 9, characterized in that: The step of testing the isolation performance of the magnetic-acoustic isolator based on the three-dimensional data specifically includes: Under the same magnetic field, calculating first difference data between three-dimensional data of forward transmission coefficient in scattering parameters and three-dimensional data of reverse transmission coefficient in scattering parameters; or Calculating second difference data between the three-dimensional data of the forward transmission coefficient in the scattering parameters under the sequential magnetic field and the three-dimensional data of the forward transmission coefficient in the scattering parameters under the reverse magnetic field; or Calculating third difference data between the three-dimensional data of the reverse transmission coefficient in the scattering parameters under the sequential magnetic field and the three-dimensional data of the reverse transmission coefficient in the scattering parameters under the reverse magnetic field; The isolation performance of the magnetic-acoustic isolator is determined based on the first difference data, the second difference data, or the third difference data.

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