A voltage-controlled adjustable spin-wave phase shifter

Abstract

The present invention provides a voltage-controlled adjustable spin-wave phase shifter, comprising: a ferromagnetic layer for transmitting spin waves as a spin-wave waveguide; an input layer and an output layer located above the ferromagnetic layer and connected to both ends of the ferromagnetic layer respectively, the input layer being used for inputting the spin waves, and the output layer being used for outputting the spin waves; a voltage-controlled layer located above the ferromagnetic layer and connected to a position between both ends of the ferromagnetic layer, the voltage-controlled layer comprising an insulating layer and a metal electrode layer, the metal electrode layer being located above the insulating layer, and the voltage-controlled layer being used for changing the phase of the spin waves by regulating one or more of the length of the metal electrode layer, the voltage, and the thickness of the insulating layer. The present invention changes the phase of the spin waves by regulating the length of the metal electrode layer, the voltage, and the thickness of the insulating layer, and has a simple structure and is easy to integrate, and can be used in spin-wave chips and the field of modern communication.

Description

Technical Field

[0001] The present invention relates to the field of spintronic technologies, and in particular, to a voltage-controlled tunable spin-wave phase shifter. Background Art

[0002] Spin is an ideal information carrier for the next generation of information technologies following the modern ones with electrons and light as information carriers. Spin waves are magnetic excited states in magnetic materials, which can effectively carry spin information and have both the advantages of waves and particle characteristics. The transmission of spin waves is based on the exchange of angular momentum and does not require the movement of electrons, so the transmission loss is small and the generated Joule heat is extremely low. At the same time, spin waves can be excited and detected through coplanar waveguides, spin-transfer torque effects, spin-orbit torque effects, etc., and are compatible with modern CMOS (Complementary Metal Oxide Semiconductor) processes.

[0003] Spin waves can store information through phase and amplitude. To construct a spin-wave chip, a spin-wave phase shifter is essential. Existing spin-wave phase-shifting technologies include the interaction between spin waves and micro-magnetic structures (such as chiral domain walls), external magnetic field regulation, etc. Most of them have disadvantages such as non-dynamic regulation or difficulty in integration, and it is difficult to move towards practical applications. Summary of the Invention

[0004] The present invention provides a voltage-controlled tunable spin-wave phase shifter to solve the defects in the prior art that the spin-wave phase shifter cannot be dynamically regulated and is difficult to integrate, and to realize a spin-wave phase shifter based on voltage regulation.

[0005] The present invention provides a voltage-controlled tunable spin-wave phase shifter, comprising:

[0006] A ferromagnetic layer, serving as a spin-wave waveguide to transmit spin waves;

[0007] An input layer and an output layer, located above the ferromagnetic layer and respectively connected to both ends of the ferromagnetic layer. The input layer is used to input the spin waves, and the output layer is used to output the spin waves. The input layer and the output layer can be coplanar waveguides, or other methods such as spin-transfer torque effects can be used to excite and detect spin waves;

[0008] A voltage-controlled layer, located above the ferromagnetic layer and connected to the upper surface of the ferromagnetic layer. The voltage-controlled layer includes an insulating layer and a metal electrode layer. The metal electrode layer is located above the insulating layer. The voltage-controlled layer is used to change the phase of the spin waves by regulating one or more of the length of the metal electrode layer, the voltage, and the thickness of the insulating layer.

[0009] According to the voltage-controlled tunable spin-wave phase shifter provided by the present invention, a substrate is further included, and the substrate is located below the ferromagnetic layer.

[0010] According to a voltage-controlled tunable spin-wave phase shifter provided by the present invention, when a voltage is applied to the metal electrode layer and the substrate is grounded, due to the voltage-controlled magnetic anisotropy effect of the voltage-controlled layer, the magnetic anisotropy of the ferromagnetic layer below the metal electrode layer changes, resulting in a change in the phase of the spin wave.

[0011] According to a voltage-controlled tunable spin-wave phase shifter provided by the present invention, the material of the ferromagnetic layer is a ferromagnetic alloy such as CoFeB.

[0012] According to a voltage-controlled tunable spin-wave phase shifter provided by the present invention, the material of the insulating layer is MgO or the like.

[0013] According to a voltage-controlled tunable spin-wave phase shifter provided by the present invention, the phase shift amount of the spin wave is proportional to the length of the metal electrode layer, the phase shift amount of the spin wave is proportional to the voltage of the metal electrode layer, and the phase shift amount of the spin wave is inversely proportional to the thickness of the insulating layer.

[0014] According to a voltage-controlled tunable spin-wave phase shifter provided by the present invention, the voltage-controlled layer is used to regulate one or more of the thickness of the insulating layer, the length and voltage of the voltage-controlled layer to change the phase of the spin wave according to the dependence relationship between the phase shift amount of the spin wave and the length, voltage of the metal electrode layer, and the thickness of the insulating layer. The dependence relationship is obtained by considering the perpendicular film system and based on the semi-classical spin-wave theory.

[0015] According to a voltage-controlled tunable spin-wave phase shifter provided by the present invention, the phase shift amount of the spin wave is determined according to the magnetic parameters of the ferromagnetic layer, the frequency of the spin wave, the magnetoelectric coefficient jointly determined by the ferromagnetic layer and the voltage-controlled layer, the thickness of the insulating layer, the length of the metal electrode layer, and the voltage of the metal electrode layer.

[0016] According to a voltage-controlled tunable spin-wave phase shifter provided by the present invention, the voltage-controlled layer is used to regulate one or more of the length, voltage of the metal electrode layer, and the thickness of the insulating layer to change the phase of the spin wave through the following formula:

[0017]

[0018] Wherein, is the phase shift amount of the spin wave, N is determined by the magnetic parameters of the ferromagnetic layer and the frequency of the spin wave, ε is the magnetoelectric coefficient jointly determined by the ferromagnetic layer and the voltage-controlled layer, d is the thickness of the insulating layer, L is the length of the metal electrode layer, and V is the voltage of the metal electrode layer.

[0019] According to a voltage-controlled tunable spin-wave phase shifter provided by the present invention, the formula for N is as follows:

[0020]

[0021] Among them, A is the exchange constant, μ 0 is the vacuum permeability, M S is the saturation magnetization, γ is the gyromagnetic ratio, ω is the spin-wave angular frequency, K i is the uniaxial anisotropy constant of each region on the left, below, and right of the ferromagnetic layer located in the voltage-controlled layer, K eff,i is the effective uniaxial anisotropy constant of the corresponding region, k i is the wave vector of the spin wave in different regions of the ferromagnetic layer. When the subscript i = 1, it represents the corresponding parameters of the region of the ferromagnetic layer on the left of the voltage-controlled layer. When the subscript i = 2, it represents the corresponding parameters of the region of the ferromagnetic layer below the voltage-controlled layer. When the subscript i = 3, it represents the corresponding parameters of the region of the ferromagnetic layer on the right of the voltage-controlled layer. The regions of the ferromagnetic layer on the left and right of the voltage-controlled layer are exactly the same.

[0022] The voltage-controlled tunable spin-wave phase shifter provided by the present invention uses a ferromagnetic layer as a spin-wave waveguide to transmit spin waves, uses the input layer and the output layer connected to both ends of the ferromagnetic layer to input and output spin waves respectively, and uses the voltage-controlled layer connected to the middle of the ferromagnetic layer to change the phase of the spin wave. The voltage-controlled layer includes an insulating layer and a metal electrode layer. Since the phase shift amount of the spin wave is related to the thickness of the insulating layer, the length of the metal electrode layer, and the voltage, the phase of the spin wave is changed by adjusting one or more of the thickness of the insulating layer, the length of the voltage-controlled layer, and the voltage. Moreover, the structure is simple and easy to integrate, and it can be used in spin-wave chips and the field of modern communication. Description of the Drawings

[0023] 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.

[0024] Figure 1 is a schematic structural diagram of the voltage-controlled tunable spin-wave phase shifter provided by the present invention;

[0025] Figure 2 is a schematic diagram showing the change of the phase shift amount of the spin wave with the length of the metal electrode layer in the voltage-controlled tunable spin-wave phase shifter provided by the present invention;

[0026] Figure 3 is a schematic diagram showing the change of the phase shift amount of the spin wave with the voltage of the metal electrode layer in the voltage-controlled tunable spin-wave phase shifter provided by the present invention;

[0027] Figure 4It is a schematic diagram showing the variation of the phase shift of the spin wave with the thickness of the insulating layer in the voltage-controlled tunable spin-wave phase shifter provided by the present invention;

[0028] Figure 5 It is a schematic diagram showing the variation of the phase shift of the spin wave with the frequency of the spin wave in the voltage-controlled tunable spin-wave phase shifter provided by the present invention. Detailed implementation manners

[0029] 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. Obviously, 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.

[0030] The following combines Figure 1 to describe a voltage-controlled tunable spin-wave phase shifter of the present invention, including:

[0031] A ferromagnetic layer, which serves as a spin-wave waveguide to transmit spin waves;

[0032] An input layer and an output layer, which are located above the ferromagnetic layer and are respectively connected to both ends of the ferromagnetic layer. The input layer is used to input the spin waves, and the output layer is used to output the spin waves;

[0033] A voltage-controlled layer, which is located above the ferromagnetic layer and is connected to the position between both ends of the ferromagnetic layer. The voltage-controlled layer includes an insulating layer and a metal electrode layer. The metal electrode layer is located above the insulating layer. The voltage-controlled layer is used to change the phase of the spin wave by regulating one or more of the thickness of the insulating layer, the length of the metal electrode layer, and the voltage.

[0034] The ferromagnetic layer is Figure 1 a light gray strip shape in the middle, located above the bottom substrate and in contact with the substrate. The ferromagnetic layer can also be called a waveguide (Wave Guide, WG) layer, which serves as a spin-wave waveguide to transmit spin waves.

[0035] Figure 1 The two green cuboids in the middle are coplanar waveguides (Coplanar Waveguide, CPW), which are located at both ends above the ferromagnetic layer. Among them, one coplanar waveguide is used for the input of spin waves, and the other coplanar waveguide is used for the output of spin waves. In this embodiment, the input layer and the output layer are taken as coplanar waveguides as an example. The input layer and the output layer can also use other methods such as the spin transfer torque effect to excite and detect spin waves.

[0036] The coplanar waveguide on the left is the first coplanar waveguide, and the coplanar waveguide on the right is the second coplanar waveguide. Or the coplanar waveguide on the left is the second coplanar waveguide, and the coplanar waveguide on the right is the first coplanar waveguide.

[0037] When the first coplanar waveguide is used for the input of spin waves, the second coplanar waveguide is used for the output of spin waves. When the first coplanar waveguide is used for the output of spin waves, the second coplanar waveguide is used for the input of spin waves.

[0038] The voltage-controlled layer is a bilayer structure located above the ferromagnetic layer, including an insulating layer and a metal electrode layer. The insulating layer is a gray cuboid located above the ferromagnetic layer, and the metal electrode layer is a yellow cuboid located above the ferromagnetic layer.

[0039] By changing one or more of the thickness of the insulating layer, the voltage V of the metal electrode layer G and the length, the phase of the spin wave can be changed. The voltage-controlled tunable spin wave phase shifter in this embodiment can be applied to logic devices.

[0040] In this embodiment, the ferromagnetic layer is used as a spin wave waveguide to transmit spin waves, the coplanar waveguides connected to both ends of the ferromagnetic layer are used to import and export spin waves, and the voltage-controlled layer connected to the middle of the ferromagnetic layer is used to change the phase of the spin wave. The voltage-controlled layer includes an insulating layer and a metal electrode layer. Since the phase shift amount of the spin wave is related to the thickness of the insulating layer, the length of the metal electrode layer, and the voltage, the phase of the spin wave is changed by regulating one or more of the thickness of the insulating layer, the length of the metal electrode layer, and the voltage. Moreover, the structure is simple and easy to integrate, and it can be used in spin wave chips and modern communication fields.

[0041] Based on the above embodiment, this embodiment further includes a substrate, and the substrate is located below the ferromagnetic layer.

[0042] Figure 1 The dark gray cuboid in the middle and bottom layer is the substrate, and the substrate is located below the ferromagnetic layer and in contact with the ferromagnetic layer.

[0043] Based on the above embodiment, when a voltage is applied to the metal electrode layer and the substrate is grounded in this embodiment, due to the voltage-controlled magnetic anisotropy effect of the voltage-controlled layer, the magnetic anisotropy of the ferromagnetic layer below the metal electrode layer changes, resulting in a change in the phase of the spin wave.

[0044] Based on the above embodiment, the material of the ferromagnetic layer in this embodiment is ferromagnetic alloy CoFeB.

[0045] Based on the above embodiment, the material of the insulating layer in this embodiment is MgO.

[0046] Based on the above embodiments, in this embodiment, the phase shift amount of the spin wave is proportional to the length of the metal electrode layer, the phase shift amount of the spin wave is proportional to the voltage of the metal electrode layer, and the phase shift amount of the spin wave is inversely proportional to the thickness of the insulating layer.

[0047] The thinner the insulating layer and the longer the length of the metal electrode layer, and the greater the voltage of the metal electrode layer, the greater the phase shift amount of the spin wave. According to the required phase shift amount of the spin wave control, the direction and degree of control of the thickness of the insulating layer, the length of the metal electrode layer, and the voltage can be determined.

[0048] Based on the above embodiments, in this embodiment, the voltage control layer is used to regulate one or more of the thickness of the insulating layer, the length of the metal electrode layer, and the voltage according to the dependence relationship between the phase shift amount of the spin wave and the thickness of the insulating layer, the length of the metal electrode layer, and the voltage, so as to change the phase of the spin wave. The dependence relationship is obtained by considering the perpendicular film system and based on the semi-classical spin wave theory. The perpendicular film does not require an external magnetic field, and the spin wave is isotropically transmitted therein, which is convenient for the preparation and application of the device.

[0049] Based on the above embodiments, in this embodiment, the phase shift amount of the spin wave is determined according to the magnetic parameters of the ferromagnetic layer, the frequency of the spin wave, the magnetoelectric coefficient jointly determined by the ferromagnetic layer and the voltage control layer, the thickness of the insulating layer, the length of the metal electrode layer, and the voltage of the metal electrode layer.

[0050] Based on the above embodiments, in this embodiment, the voltage control layer is used to regulate one or more of the length of the metal electrode layer, the voltage, and the thickness of the insulating layer through the following formula to change the phase of the spin wave:

[0051]

[0052] where, is the phase shift amount of the spin wave, N is determined by the magnetic parameters of the ferromagnetic layer and the frequency of the spin wave, ε is the magnetoelectric coefficient jointly determined by the ferromagnetic layer and the voltage control layer, d is the thickness of the insulating layer, L is the length of the metal electrode layer, and V is the voltage of the metal electrode layer.

[0053] Based on the above embodiments, the formula for N in this embodiment is as follows:

[0054]

[0055]

[0056] where, A is the exchange constant, μ 0 is the vacuum permeability, M Sis the saturation magnetization, γ is the gyromagnetic ratio, ω is the angular frequency of the spin wave. K i is the uniaxial anisotropy constant of each region located on the left, below, and right of the voltage-controlled layer in the ferromagnetic layer, K eff,i is the effective uniaxial anisotropy constant of the corresponding region, k i is the wave vector of the spin wave in different regions of the ferromagnetic layer. When the subscript i = 1, it represents the corresponding parameters of the region of the ferromagnetic layer located on the left of the voltage-controlled layer. When the subscript i = 2, it represents the corresponding parameters of the region of the ferromagnetic layer located below the voltage-controlled layer. When the subscript i = 3, it represents the corresponding parameters of the region of the ferromagnetic layer located on the right of the voltage-controlled layer. The regions of the ferromagnetic layer located on the left and right of the voltage-controlled layer are exactly the same.

[0057] The specific derivation process of the dependence of the phase shift of the spin wave on the thickness of the insulating layer, the length of the metal electrode layer, and the voltage is as follows:

[0058] The dynamic behavior of the magnetic moment is determined by the LLG (Landau-Lifshitz-Gilbert) equation:

[0059]

[0060] To simplify the calculation, the damping term is ignored. The effective field satisfies the following equation:

[0061]

[0062] Among them, the first term is the effective anisotropy field, The second term is the exchange field. M s , γ, A, μ 0 , α are the saturation magnetization, gyromagnetic ratio, exchange constant, vacuum permeability, and damping factor respectively, H eff is the effective field, m is the normalized magnetization of the ferromagnetic layer, m z is the z-component of the magnetic moment, is the Hamiltonian operator, is the unit vector in the z direction.

[0063] At steady state, due to the existence of perpendicular magnetic anisotropy, m = (0, 0, 1). After exciting the spin wave, assume Substituting Equation (2) into Equation (1), it can be deduced that:

[0064]

[0065] Let ψ = iu + v = φe -iωt , there is:

[0066]

[0067] When a voltage is applied, the magnetic anisotropy of the ferromagnetic layer below the metal electrode layer changes, while other regions remain unchanged. Assume that the starting position of the metal electrode layer is x = a, the ending position is x = b, and the entire length is L. The entire ferromagnetic layer can be divided into three parts: the left side (x < a), the voltage-controlled region, and the right side (x > b). Assume that the input spin wave on the left side is The spin wave in the voltage-controlled region is The output spin wave on the right side is According to the continuity of the wave function and the continuity of the first derivative of the wave function, it can be deduced that:

[0068]

[0069] The left and right sides are exactly the same, k 1 = k 3 Then, equation (6) can be simplified to:

[0070]

[0071] From equations (3) and (4), the dispersion relation of spin wave transmission can be deduced:

[0072]

[0073] If the change in magnetic anisotropy under the action of the electric field is small and the corresponding change in wave vector is very small, substituting equation (8) into equation (7) and ignoring the high-order terms, it can be simplified to:

[0074]

[0075] Among them, is determined by the magnetic parameters of the material and the frequency of the spin wave. ε is the magnetoelectric coefficient, d is the thickness of the insulating layer, and L is the length of the electrode. Obviously, the spin wave phase shift is proportional to the product of the electric field strength and the electrode length, and inversely proportional to the thickness of the insulating layer.

[0076] Simulations were carried out using the micromagnetic simulation software OOMMF (Object Oriented Micromagnetic Framework). The specific results are as Figures 2 to 5 shown. It shows that by changing the applied voltage, electrode length, and insulating layer thickness, the phase of the spin wave can be accurately linearly regulated within a large range and is satisfied within a very large frequency bandwidth.

[0077] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended 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 described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A voltage-controlled adjustable spin wave phase shifter, characterized in that: include: The ferromagnetic layer acts as a spin wave guide to transmit spin waves; An import layer and an export layer, located above the ferromagnetic layer and connected to two ends of the ferromagnetic layer respectively, the import layer is used to import the spin wave, the export layer is used to export the spin wave, and the import layer and the export layer are coplanar waveguides; A voltage control layer, located above the ferromagnetic layer and connected to a position between two ends of the ferromagnetic layer, the voltage control layer comprises an insulating layer and a metal electrode layer, the metal electrode layer is located above the insulating layer, and the voltage control layer is used to change the phase of the spin wave by regulating one or more of the length and voltage of the metal electrode layer and the thickness of the insulating layer; The phase shift of the spin wave is determined according to the magnetic parameters of the ferromagnetic layer, the frequency of the spin wave, the magnetoelectric coefficient determined by the ferromagnetic layer and the voltage-controlled layer, the thickness of the insulating layer, the length of the metal electrode layer and the voltage of the metal electrode layer; The voltage-controlled layer is used to change the phase of the spin wave by regulating one or more of the length, voltage of the metal electrode layer and the thickness of the insulating layer through the following formula: in, is the phase shift of the spin wave, N is determined by the magnetic parameters of the ferromagnetic layer and the frequency of the spin wave, ε is the magnetoelectric coefficient determined by the ferromagnetic layer and the voltage-controlled layer, d is the thickness of the insulating layer, L is the length of the metal electrode layer, and V is the voltage of the metal electrode layer; The formula for N is as follows: Where A is the exchange constant, μ0 is the vacuum magnetic permeability, M S is the saturation magnetization, γ is the gyromagnetic ratio, ω is the angular frequency of the spin wave, K i is the uniaxial anisotropy constant of the regions in the ferromagnetic layer located on the left, below and right of the pressure control layer, K eff,i is the effective uniaxial anisotropy constant of the corresponding region, k i are the wave vectors of the spin waves in different regions of the ferromagnetic layer. When the subscript i=1, it indicates the corresponding parameters of the ferromagnetic layer located in the left region of the pressure control layer. When the subscript i=2, it indicates the corresponding parameters of the ferromagnetic layer located below the pressure control layer. When the subscript i=3, it indicates the corresponding parameters of the ferromagnetic layer located in the right region of the pressure control layer. The regions where the ferromagnetic layer is located on the left and right of the pressure control layer are exactly the same.

2. The voltage-controlled adjustable spin wave phase shifter according to claim 1, characterized in that: Also included is a substrate located below the ferromagnetic layer.

3. The voltage-controlled adjustable spin wave phase shifter according to claim 2, characterized in that: When a voltage is applied to the metal electrode layer and the substrate is grounded, due to the voltage-controlled magnetic anisotropy effect of the voltage-controlled layer, the magnetic anisotropy of the ferromagnetic layer below the metal electrode layer changes, resulting in a change in the spin wave phase.

4. The voltage-controlled adjustable spin wave phase shifter according to claim 1, characterized in that: The material of the ferromagnetic layer is ferromagnetic alloy CoFeB.

5. The voltage-controlled adjustable spin wave phase shifter according to claim 1, characterized in that: The material of the insulating layer is MgO.

6. The voltage-controlled adjustable spin wave phase shifter according to claim 1, characterized in that: The phase shift of the spin wave is proportional to the length of the metal electrode layer, the phase shift of the spin wave is proportional to the voltage of the metal electrode layer, and the phase shift of the spin wave is inversely proportional to the thickness of the insulating layer.

7. The voltage-controlled adjustable spin wave phase shifter according to claim 1, characterized in that: The voltage-controlled layer is used to change the phase of the spin wave by regulating one or more of the thickness of the insulating layer, the length of the metal electrode layer and the voltage according to the dependence of the phase shift of the spin wave on the length of the metal electrode layer, the voltage and the thickness of the insulating layer. The dependence takes into account the vertical film system and is obtained based on the semiclassical spin wave theory.

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