RU2813745C1 - Controlled space-frequency filter of microwave signal on spin waves - Google Patents

Abstract

FIELD: radio engineering.

SUBSTANCE: invention relates to microwave radio engineering, in particular to devices based on magnetostatic waves, and can be used as a frequency filter of microwave signal on spin waves. Technical problem to be solved by the invention is to improve the design of the spin-wave filter controlled by an external magnetic field. Disclosed device is a microwave guiding structure placed in a magnetic field, which contains substrate 1 from GGG film, on which there is a microwave guide for surface magnetostatic waves (SMSW), made in the form of a two-layer ferromagnetic film of yttrium iron garnet (YIG). First upper layer of microwave guide 2 has the shape of a meander formed by a set of periodic grooves forming a magnon crystal. Second inner layer of microwave guide 3 is placed on substrate 1. At the ends of the first layer of microwave guide 2 there are microstrip converters 4, 5 for excitation and reception of magnetostatic waves. Layers 2, 3 have different saturation magnetisation.

EFFECT: providing the possibility of operating modes adjustment.

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Description

Field of technology

The invention relates to microwave radio engineering, in particular to devices using magnetostatic waves and can be used as a frequency filter for a microwave signal on spin waves.

State of the art

It is known that a large number of devices for processing signals on magnetostatic waves can be implemented on the basis of magnon crystals - artificial periodic structures containing a magnetically ordered component (S.A. Nikitov et al. “Magnonics - a new direction of spintronics and spin-wave electronics”, UFN , 185:10 (2015), 1099-1128).

A device based on magnetostatic waves is known (patent US 7528688, IPC H01P 1/19, published 05/05/2009), which contains a gallium-gadolinium garnet substrate, a piezoelectric layer, a YIG film located between them, input and output electrodes. In this case, the electric field in the piezoelectric layer creates magnetostriction, and the additional magnetic field in the ferrite layer causes a change in the resonant frequency, thereby adjusting the operating frequency. This type of structure can be used as microwave resonators, bandpass filters and delay lines.

The disadvantage of this device is the inability to control the properties of the spin wave spectrum by changing the external magnetic field.

A non-reciprocal tunable bandpass filter is known (application WO2014052913, IPC H01P1/20, published 04/03/2014), including a converter containing parallel connected conductive lines and a ferrite layer, so that the parallel edges of the ferrite layer are inclined at a non-zero angle Θ relative to the parallel conjugate microstrip lines of the microstrip converter Thanks to this design, the surface wave reflected from the side faces of the ferrite film is converted back into a volume wave without forming a standing wave, and therefore does not enter the output signal. Thus, non-reciprocal filtering of spin waves is carried out, which makes it possible to suppress side modes formed due to spatial resonance in mutual filters, but introduces significant losses, which is a disadvantage of this device.

A frequency filter based on a magnon crystal is known, used to control the frequency of spin waves (patent US8487391, IPC H01L29/82, published 07/16/2013). The device consists of a waveguide based on a thin magnetic film. The waveguide has three sections, one of which is a periodic structure - a magnon crystal, formed by periodically changing the width or thickness of a ferromagnetic film.

The disadvantage of this device is the inability to operate in dual-frequency bands. http://www1.fips.ru/fips_servl/BiEndhttp://www1.fips.ru/fips_servl/AbStart

The closest to the patented device is a functional magnonics device on a multilayer ferromagnetic structure (patent RU2702915, IPC H01P1/218, published 10/14/2019), containing a non-magnetic dielectric substrate, ferromagnetic layers of yttrium iron garnet (YIG), microstrip converters for excitation and reception of MSW , a source of magnetic field, while it is made in the form of a multilayer 3D structure, including external and internal ferromagnetic layers, separated from each other by a layer of non-magnetic substance and located one above the other, the surface of the substrate in cross-section has the shape of a meander formed by a set of periodic grooves, the longitudinal axis which is perpendicular to the direction of propagation of the MSW, the outer and inner ferromagnetic layers have a period coinciding with the period of the protrusions, side faces and grooves formed by grooves on the surface of the substrate, and the magnetic field of the magnetic field source is oriented perpendicular to the plane of the substrate with the possibility of excitation in both ferromagnetic layers of bulk MSWs. The disadvantage of this device is the small thickness of the YIG films, the low saturation magnetization of the films, resulting in a small frequency range of the device.

Essence Revealing

The technical problem to be solved by the invention is to improve the design of a spin-wave filter controlled by an external magnetic field, namely to create a controlled spatial-frequency filter for a microwave signal by changing the configurations of the external magnetic field.

The technical result is to provide the ability to control operating modes.

The technical result is achieved by the fact that in the spatial-frequency filter of the microwave signal, containing a microwave guide made of yttrium iron garnet placed on a gallium-gadolinium substrate, the outer surface of which has a meander-shaped cross-section formed by a set of periodic grooves, microstrip converters for exciting and receiving magnetostatic spin waves, the source of the magnetic field, according to the solution, the microwave guide is a two-layer film, the layers of which have different saturation magnetization, microstrip converters are placed at the ends of the outer surface of the microwave guide, and the magnetic field of the magnetic field source is oriented in the plane of the substrate with the possibility of exciting surface magnetostatic spin waves in both layers.

The patented controlled spatial-frequency filter of a microwave signal on spin waves contains a substrate made of a non-magnetic dielectric, a two-layer ferrite film (FP) placed on the substrate, made of yttrium iron garnet with different magnetization, an external magnetic field is used as a control element, input and output converters of magnetostatic waves . The external magnetic field of the magnetic field source is oriented perpendicular to the length of the substrate plane.

Brief description of drawings

The invention is illustrated by drawings, where: FIG. 1 - device design; Fig 2 - design, side view; fig. 3 - dispersion characteristic for the high-frequency region of the MSSW with positive magnetization of the external magnetic field; fig. 4 - dispersion characteristic for the low-frequency region of the MSSW with positive magnetization of the external magnetic field; fig. 5 - dispersion characteristic for the high-frequency region of the MSSW with negative magnetization of the external magnetic field; fig. 6 - dispersion characteristic for the low-frequency region of the MSSW with negative magnetization of the external magnetic field.

The positions in the drawing indicate:

1 - gallium gadolinium garnet (GGG) substrate;

2 - first layer of microwave guide;

3 - second layer of microwave guide;

4 - microstrip converter for excitation of MSSW;

5 - microstrip converter for receiving PMSV;

d ₁ - thickness of the second layer of the microwave guide;

d ₂ - thickness of the first layer of the microwave guide;

S is the width of microstrip converters;

w ₀ is the width of the film under the microstrip converter;

w ₁ - groove length;

w ₂ - protrusion length;

Δd is the depth of the grooves;

L - substrate length;

H ₀ - external magnetic field;

k (cm ^-1 ) - wave number.

Carrying out the invention

The inventive device is a microwave guide structure placed in a magnetic field, which contains a substrate made of GGG 1 film, on which a microwave guide for surface magnetostatic waves (MSW), made in the form of a two-layer ferromagnetic film of yttrium iron garnet (YIG), is placed. The first upper layer of the microwave guide 2 has a meander-shaped cross-section formed by a set of periodic grooves forming a magnon crystal. The second inner layer of the microwave guide 3 is placed on the substrate 1. At the ends of the first layer of the microwave guide 2 there are microstrip converters 4, 5 for exciting and receiving magnetostatic waves. In this case, layers 2, 3 have different saturation magnetization.

The operating mode of the controlled spatial-frequency filter of the microwave signal on spin waves is determined by the selected parameters of MSSW propagation: the period of the magnon crystal, the magnitude and direction of the external magnetic field. Thus, the frequency range depends on the external magnetic field; by changing the period of the magnon crystal, due to phase matching, it is possible to control the passage of spin waves and the formation of band gaps.

The principle of operation of this device is that the input microwave signal, the frequency of which must lie in the frequency range determined by the value of H ₀ external constant magnetic field, is supplied to the input microstrip converter 4. Next, the microwave signal is converted into a surface magnetostatic wave (MSW), propagating along the microwave guide 2, 3. The nature of the propagation of spin waves will depend on the period of the magnon crystal 2 and the external magnetic field. The direction of the magnetic field in the plane of the film will determine the nature of the signal transmission. Due to the presence of a magnon crystal (MC), frequency bands of signal failure and band gaps (GBZ) appear in the device.

The substrate 1 may have the following dimensions: width 100 μm, length L 1300 μm, thickness 50 μm. The thickness of the first layer 2 is 8.9 microns and has a saturation magnetization of 1738 Gas, the thickness of the second layer 3 is 6.9 microns, and the saturation magnetization is 940 Gas. The groove depth Δd is equal to 1 μm with lengths w ₁ and w ₂ equal to 100 μm. The width S of the microstrip converters 4, 5 is 30 μm. The external magnetic field H ₀ is directed parallel to the x axis (see Fig. 1).

In fig. Figures 3-6 show the results of numerical simulation. The dispersion characteristics of the MSSW device are shown, which were obtained by solving the system of Maxwell's equations using the finite element method. In the microwave structure, both HF and LF signal transmission bands are observed simultaneously. In fig. 3-6 it is clear that when the polarization of the field changes, the dispersion characteristics change greatly, especially in the low-frequency range, which characterizes the strong non-reciprocal behavior of spin waves in a two-layer structure. Due to the presence of periodically changing geometric parameters on the surface, that is, a magnon crystal, forbidden zones are formed on the dispersion characteristic in the HF range (GB, in Fig. 3, 5). Periodization of the structure makes it possible to obtain forbidden bands, depending on the MC period, at different wave numbers, and due to the non-reciprocal behavior of spin waves, the frequency at which the forbidden band appears will be different. If the external magnetic field is rotated 180 degrees, then localization of the MSSW will occur in the opposite film, which will change the transmittance of the device, which is illustrated in Fig. 3, 5 for the high-frequency region and in Fig. 4, 6 for the low-frequency region.

The device works as follows.

As described above, it is possible to implement several operating modes that can be controlled by changing the configuration of the internal magnetic field distribution when varying the magnitude and direction of the external magnetic field. The field configuration can be changed by changing the magnitude and direction of the external magnetic field. If the external magnetic field is rotated 180 degrees, then localization of the MSSW will occur in the opposite layer, which will change the transmittance of the device. Consequently, it is possible to control the operating modes of this device by changing the direction and magnitude of the external magnetic field.

Thus, the presented data confirm the achievement of a technical result, namely the creation of a controlled spatial-frequency filter for a microwave signal on spin waves, in which operating modes can be controlled by changing the configuration of the external magnetic field.

Claims (1)

A spatial-frequency filter of a microwave signal containing a microwave guide made of yttrium iron garnet placed on a gallium-gadolinium substrate, the outer surface of which has a cross-sectional shape of a meander formed by a set of periodic grooves, microstrip converters for excitation and reception of magnetostatic spin waves, a magnetic field source, characterized in that that the microwave guide is a two-layer film, the layers of which have different saturation magnetizations, microstrip converters are placed at the ends of the outer surface of the microwave guide, and the magnetic field of the magnetic field source is oriented in the plane of the substrate with the ability to excite surface magnetostatic spin waves in both layers.