RU2786486C1 - Controlled delay line on exchanged spin waves - Google Patents

Abstract

FIELD: radio engineering.

SUBSTANCE: invention relates to radio engineering and can be used in transmitting and receiving radio devices and phased antenna arrays in the microwave range. This effect is achieved by the fact that the controlled delay line on spin waves, containing an epitaxial ferrite film of yttrium iron garnet, YIG, located on a non-magnetic layer of gallium-gadolinium garnet, GGG, microstrip microwave signal converters and a magnetizing field source, according to the invention additionally contains the second non-magnetic GGG layer, located on the surface of the YIG on the opposite side from the first, forming a three-layer structure GGG-YIG-GGG, and also contains two metallized dielectric substrates, one of which contains the input converter of the microwave signal, and the second - the output converter, they are located in the same plane so that their longitudinal axes coincide, the GGG-YIG-GGG structure is installed in a gap formed so that the end surfaces of the non-magnetic GGG layers adjoin the ends of the dielectric substrates and the ends of the converters, the magnetizing field is oriented normal to the surface of the film YIG.

EFFECT: reducing the size of the delay line while reducing the loss of the useful signal for the conversion of wave types.

1 cl, 8 dwg

Description

The invention relates to radio engineering and can be used in transmitting and receiving radio devices and phased antenna arrays in the microwave range.

In epitaxial ferrite films of yttrium iron garnet (YIG) grown on a nonmagnetic gadolinium gallium garnet (GGG) substrate, two types of spin waves, dipole and exchange spin waves, can be excited.

Dipole spin waves (in the literature they are often referred to as magnetostatic waves (MSWs)) propagate due to the long-range dipole-dipole interaction. Depending on the direction of the magnetizing field in the film, direct volumetric, reverse volumetric and surface MSWs can be excited (Gurevich A.G. Ferrites at microwave frequencies. M: Fizmatgiz, 497 p.).

Exchange spin waves (ESWs) propagate due to short-range exchange interaction (Akhiezer A.I., Baryakhtar V.G., Peletminsky S.V. Spin waves. - M.: Nauka, 1967, 368 p.). The strongest exchange interaction forms an ordered structure of spin moments in the crystal, which manifests itself in the form of spontaneous magnetization of the ferrite. In the continuum approach, both types of spin waves are represented in the same way, in the form of precession waves of the spontaneous magnetization vector, and differ only in length. Waves with lengths λ: 10-1000 microns are considered to be mainly dipole, and with lengths λ≤1 micron, mainly exchange. Exchange spin waves are the most attractive, since their propagation velocities v : λ are several orders of magnitude lower than the MSW velocity.

However, relatively long-wavelength magnetostatic waves have found the widest application. This became possible due to the simplicity of their excitation and reception by microstrip (MSL) microwave signal converters. Based on the MSW, a number of radio signal processing devices were proposed in the frequency range from units to tens of GHz (Nikitov V.A., Nikitov S.A. Research and development of devices based on magnetostatic spin waves. - Foreign radio electronics, 1981, No. 2, C 41-52.). In particular, variants of the design of controlled delay lines (DL) of the microwave signal were proposed.

Known controllable delay line on the MSV (see patent US 4400669, according to class IPC H03N 2/00, pub. 08/23/1983), consisting of a magnetized YIG film, input and output MSL microwave signal converters and a metal screen located between the converters . The delay time in such a DL is adjusted by changing the gap between the YIG film and the metal screen.

Known controlled delay line on the MSV (see USSR author's certificate No. 1552958, according to class MPK H01R 1/215, pub. 01/27/2001), consisting of a magnetized YIG film, input and output MSL converters located on separate dielectric substrates. Adjustment of the delay time in such a DL is carried out by changing the path length of the MSW with a relative shift of one of the MSL converter substrates.

A controlled delay line on surface MSFs is also known (see RF patent No. 2594382, according to class IPC H03N 9/38, published 08/20/2016), consisting of a tangentially magnetized YIG film with a periodic structure of etched grooves, input and output MSL converters. The delay time in such a DL is adjusted by rotating the YIG film in the transducer location plane.

The disadvantage of these devices is the mechanical adjustment of the delay time.

Closest to the claimed solution is a controlled delay line on the MCB with electrical adjustment of the delay time of the microwave signal (see US patent No. 3935550, according to class IPC H03H 7/14, pub. garnet YIG on a layer of gallium-gadolinium garnet GGG, input and output microwave signal converters and a source of magnetizing field controlled by current.

The disadvantage of the prototype is the use to delay the microwave signal relative to the long-wavelength dipole spin (magnetostatic) waves.

The problem to be solved by the invention is to create a controlled delay line on ultrashort exchanged spin waves.

The technical result of the invention is to reduce the size of the delay line while reducing the loss of the useful signal for the conversion of wave types.

This technical result is achieved by the fact that the controlled delay line on spin waves, containing an epitaxial ferrite film of yttrium iron garnet YIG, located on a non-magnetic layer of gallium-gadolinium garnet GGG, input and output microwave signal converters and a current-controlled magnetizing field source, according to the invention , additionally contains a second non-magnetic layer of gallium-gadolinium garnet GGG, located on the surface of the film of yttrium iron garnet on the opposite side of the first one, forming a three-layer structure GGG-YIG-GGG, and also contains two dielectric substrates, one of which contains a microwave input converter -signal, and on the second - the output converter, the converters are made of microstrip and are located in the same plane so that their longitudinal axes coincide, the GGG-YIG-GGG structure is installed in the gap formed by dielectric substrates and converters so that the end surfaces are non-magnetic layers of gallium gadolinium garnet are adjacent to the ends of the dielectric substrates and to the ends of the converters, the dielectric substrates on the sides opposite to the converters are metallized, the magnetizing field is oriented along the normal to the surface of the YIG film.

The invention is illustrated by drawings, which shows:

- figure 1 design of a controlled delay line on the exchange spin waves;

и

- векторы электрической и магнитной составляющих падающей и прошедшей плоской электромагнитной ТЕМ волны, распространяющихся в направлении волнового вектора

, волнистой стрелкой показано направление распространения ОСВ, прямой стрелкой показано направление намагничивающего поля

;- figure 2 three-layer structure GGG-YIG-GGG, where d is the thickness of the YIG film,

and

- vectors of the electric and magnetic components of the incident and transmitted plane electromagnetic TEM waves propagating in the direction of the wave vector

, the wavy arrow shows the direction of WWS propagation, the straight arrow shows the direction of the magnetizing field

;

- figure 3 graph of the distribution of spontaneous magnetization through the thickness of the YIG film;

- figure 4 3d graph of the dispersion law WWS, calculated at a fixed value of the magnetizing field;

- figure 5 graphs of the frequency dependence of the delay time and the phase of the transmitted signal, calculated at a fixed value of the magnetizing field;

- Fig.6 shows graphs of the field dependence of the delay time and the phase of the transmitted signal, calculated at a fixed value of the frequency of the microwave signal;

- Fig.7 portable adjustable current magnetic system for implementing the invention: a - side view, b - top view in section;

- in Fig.8 is a graph of the distribution of the magnetizing field H ₀ in the cross section of the working gap of the magnetic system, in the insert is a picture of the magnetic field lines inside and outside the working gap.

In the drawings, positions indicate:

1 - input MSL converter, 2 - first non-magnetic layer of gallium-gadolinium garnet GGG, 3 - epitaxial ferrite film of yttrium iron garnet YIG, 4 - second non-magnetic layer GGG, 5 - output MSL converter, 6, 7 - dielectric substrates, 8, 9 - metallizing layers of dielectric substrates, 10, 11 - diffusion layers of the YIG film, 12, 13 - steel poles of the magnetic system, 14, 15 - permanent magnets (arrows indicate the direction of residual magnetization), 16, 17 - electric control coils.

The controlled delay line on exchange spin waves contains (see figure 1) an epitaxial ferrite film of yttrium iron garnet YIG 3, on opposite sides of which there are non-magnetic layers of gallium-gadolinium garnet GGG 2 and 4, forming the structure GGG-YIG-GGG. The delay line also contains input 1 and output 5 MSL converters located on dielectric substrates 6 and 7. The GGG-YIG-GGG structure is installed in the gap formed by dielectric substrates 6 and 7 and converters 1 and 5 gadolinium garnet 2 and 4 are adjacent to the ends of the dielectric substrates and to the ends of the converters.

The device works as follows.

On the surface of a normally magnetized film YIG 3 falls flat electromagnetic TEM wave (see figure 2), which within the thickness of the diffusion layer 10 is converted into a short-wave exchanged spin wave (OSW). Further, WWS propagates in the homogeneous part of the film and in the diffusion layer 11 is converted back into an electromagnetic wave. The delay of the transmitted microwave signal is determined by the path length and the WWS propagation velocity.

Taking into account the fact that the WWS speed is several orders of magnitude less than the MSW speed, the run length and, accordingly, the dimensions of the delay line at the WWS decrease in proportion to the speed ratio. In addition, within the thickness of the diffusion layer, the effects of collinear interaction of coupled waves arise, in which a long-wavelength electromagnetic wave smoothly transforms into a short-wavelength exchange spin wave and vice versa. In this case, there is no reflection of waves at the boundaries of the YIG film, which significantly reduces the loss of the useful signal for matching wave types.

The conversion of electromagnetic and exchange spin waves is due to the magnetic inhomogeneity of the diffusion layers, which is always formed during epitaxial growth due to the diffusion of nonmagnetic Gd ³⁺ , Ga ³⁺ ions of the GGG substrate (Gd ₃ Ga ₅ O ₁₂ ), which partially replace the magnetic Y ³⁺ ions, Fe ³⁺ films YIG (Y ₃ Fe ₅ O ₁₂ ) [Mitra A., Cespedes O., Ramasse Q., AN M., Marmion S., Ward M., Brydson RMD, Kinane CJ, Cooper JFK, Langridge S. , Hickey BJ Interracial Origin of the Magnetization Suppression of Thin Film Yttrium Iron Garnet.//Scientific Reports. 2017. Vol.7, P.11774. doi.org/10.1038/s41598-017-10281-6].

где σ - феноменологический параметр распределения, z - координата в поперечном направлении пленки ЖИГ. С учетом этого в трехслойной структуре ГГГ-ЖИГ-ГГГ распределение спонтанной намагниченности по толщине пленки ЖИГ описывается формулойAccording to the theory of diffusion in solids ([H. Mehrer. DiffusioninSolids: Fundamentals, Methods, Materials, Diffusion-Controlled Processes. Springer: 2007. 651 p.), the concentration distribution of magnetic ions in the diffusion layer is described by the Gaussian function

where σ is the phenomenological distribution parameter, z is the coordinate in the transverse direction of the YIG film. Taking this into account, in the GGG-YIG-GGG three-layer structure, the distribution of spontaneous magnetization over the thickness of the YIG film is described by the formula

where M ₀ is the uniform magnetization of the film outside the diffusion layer, d is the thickness of the YIG film. Graph of the distribution of magnetization M(z), calculated for given film parameters YIG M ₀ =140G, d=10 μm, σ=10 ^-5 cm is shown in Fig.3.

The distribution function of the magnetization M (z) was used in the calculation of the dispersion law of the OSW k _S (ƒ, H ₀ , z), where k _S is the wave number of the OSW, ƒ is the frequency of the microwave signal, H ₀ is the strength of the magnetizing field (Tikhonov VV, Litvinenko AN Exchange spin waves and their application for diagnostics of the layered structure of epitaxial YIG films.// J. Magn. Magn. Mater. 2020. Vol.515. P.167241. https://doi.org/10.1016/j. jmmm.2020.167241).

Figure 4 presents a 3d-plot of the dispersion law k _S (ƒ, z), calculated at a fixed field H ₀ =5Ke. It can be seen that, within the limits of the thicknesses of the diffusion layers, the wave numbers of the WWW gradually increase (decrease) by five to six orders of magnitude. At the same time, at the boundaries of the YIG film, at z=0 and z=d, the condition for matching the WWS with the incident and transmitted electromagnetic wave k _S (ƒ, 0) = k ₀ (ƒ) and k _S (ƒ, d) = k ₀ ( ƒ), and, as can be seen in figure 4, the condition of matching and, accordingly, the effective excitation of WWS is performed in a fairly wide frequency band Δƒ ≈ 5GHz.

нетрудно было рассчитать время задержки

и набег фазы

прошедшего СВЧ-сигнала на длине пробега ОСВ

Using the dispersion law

it was not difficult to calculate the delay time

and phase advance

of the transmitted microwave signal over the length of the WWS run

For example, figure 5 shows the frequency dependence of the delay time τ (ƒ) and the phase shift ϕ (ƒ), calculated at a fixed field H ₀ =5KE.

Figure 6 shows the field dependence of the delay time τ (H ₀ ) and the phase shift ϕ(H ₀ ), calculated at a fixed frequency ƒ = 12 GHz.

Below is an example implementation of the invention.

The sample structure GGG-YIG-GGG has overall dimensions of 1×1×0.5 mm. The sample of the structure is installed in the gap of the MSL converters made on a metallized dielectric substrate 1 mm thick. The structure sample together with the input and output MSL converters is placed in the working gap of the portable magnetic system so that the magnetizing field is orthogonal to the surface of the YIG film (see Fig.7). The magnetic system includes a pair of rectangular steel poles made of St.1008 steel measuring 6×10×10 mm and a pair of rectangular NdFe35 neodymium magnets measuring 8×4×10 mm. The poles of the magnets are adjacent to the steel poles. In this case, a working gap is formed in the gap between the poles, sufficient to accommodate the GGG-YIG-GGG structure together with the transducers.

Figure 8 presents the results of a numerical calculation of the magnetic field in the working gap of a portable magnetic system. The calculations were carried out by the finite element method using the Ansoft Maxwell SV software package. The initial data for the calculation were the geometric dimensions of the elements of the magnetic system, the magnetization curve of steel St. 1008 and the residual induction of neodymium magnets, equal to 1.2T. The graph of Fig.8 shows the topology of the magnetizing field in the working gap of the magnetic system. The inset of Fig. 8 shows the pattern of magnetic field lines inside and outside the operating gap. It can be seen that inside the working gap, the magnetic field generated by the permanent magnets is almost uniform. In this case, the additional fields created by the electric control coils do not violate the field uniformity.

Claims (1)

Controlled delay line on spin waves, containing an epitaxial ferrite film of yttrium iron garnet, YIG, located on a non-magnetic layer of gallium-gadolinium garnet, GGG, input and output microwave signal converters and a current-controlled magnetizing field source, characterized in that it additionally contains the second non-magnetic layer of gallium-gadolinium garnet, GGG, located on the surface of the film of yttrium iron garnet on the opposite side from the first, forming a three-layer structure GGG-YIG-GGG, and also contains two dielectric substrates, one of which contains an input microwave signal converter , and on the second - the output converter, the converters are made of microstrip and are located in the same plane so that their longitudinal axes coincide, the GGG-YIG-GGG structure is installed in the gap formed by the dielectric substrates and converters so that the end surfaces of the non-magnetic layers of gallium-gadolinium garnet junction They are attached to the ends of the dielectric substrates and to the ends of the converters, the dielectric substrates on the sides opposite to the converters are metallized, the magnetizing field is oriented along the normal to the surface of the YIG film.

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