Three-terminal nanoscale spin wave logic device realized based on magnetic domain wall transmission mode

Abstract

The invention discloses a three-terminal nanoscale spin wave logic device realized based on a magnetic domain wall transmission mode, belongs to the technical field of magnetic vibrator devices, and aims to solve the problems that a conventional spin wave transmission device is large in design size, relatively narrow in transmittable wave frequency range, difficult to pass through a bent channel and the like. The in-plane magnetized pinning layer is coupled below the magnetic waveguide film layer with the perpendicular magnetic anisotropy, and the magnetic moment arrangement on the two sides of the magnetic domain wall channel in the waveguide layer is regulated and controlled by utilizing the magnetization orientation of the pinning layer, so that the T-shaped three-end spin wave device formed by the transverse domain wall channel and the longitudinal domain wall channel is formed. The logic device provided by the invention not only can obtain very strong spin wave intensity, so that information can be transmitted in a longer distance, but also allows spin wave transmission to pass through a sharp vertical path, so that the device can be integrated in a complex circuit.

Description

Technical Field

[0001] The present invention belongs to the technical field of quantum mechanics, and in particular relates to a three-terminal nanoscale spin wave logic device realized based on a magnetic domain wall transmission mode. Background Art

[0002] Magnetic waveguide materials can realize the transmission of spin waves (SWs). Using spin waves as information carriers to design magnetic logic devices and reconfigurable signal transmission pathways is an emerging concept with potential application value in the development of unconventional computing applications, and is therefore widely studied. Compared with traditional microelectronics technology based on current control, the main advantage of spin wave devices is that there is no Joule heat generated by charge flow, so their energy loss is very low; at the same time, the carrier signal can be identified by different characteristics of the spin wave, such as: amplitude, phase, propagation direction and wave coherence information. Therefore, effective control of spin wave transmission is of great research significance for designing high-performance magnon pathways with unique functions.

[0003] The conventional scheme for the excitation of spin waves is to connect a magnetic thin film waveguide with a spin wave transmitting antenna, and use the electromagnetic microwaves and oscillating current in the antenna to drive the magnetic charges in the magnetic waveguide to vibrate, and then propagate along the waveguide channel under the exchange and dipole action between the magnetic charges. However, the spin waves excited in this way still have disadvantages, mainly including: the excitation frequency is not easy to control, the additional bias magnetic field and the transmission wavelength greater than the micron level limit the miniaturization of waveguide devices. A more reliable solution to these problems is to use the magnetic domain wall with a line width of the nanometer level as the transmission channel of the spin wave. The magnetic domain wall is the local transition region between magnetic domains in ferromagnetic materials, and its size ranges from a few nanometers to hundreds of nanometers in width. Due to the non-collinear magnetic moment arrangement in the magnetic domain wall, the local effective field of the medium is effectively reduced, so that the region forms an energy potential well. Not only does it broaden the frequency range of spin waves that can be transmitted, but it also makes it possible to obtain spin waves with nanometer wavelengths. In addition, the reconfigurability and channel effect of the magnetic domain wall channel can significantly reduce the scattering and coherent decomposition of energy in wave transmission, making it more adaptable to complex and curved transmission paths. These characteristics provide important research and development ideas for the application of spin waves in the development of nanoscale signal processors with wide compatibility.

[0004] In summary, the research on waveguide channels based on magnetic domain walls is very beneficial to the practical application of micro spin wave devices. However, how to achieve the construction of reconfigurable magnetic domain walls and design feasible magnetic domain wall-based spin wave logic devices without external field assistance still requires further exploration. Summary of the invention

[0005] Technical problem solved by the present invention: In view of the problems of previous spin wave transmission devices, such as large design size, narrow transmittable wave frequency range and difficulty in passing through curved channels, a scheme for transmitting spin waves through a reconfigurable magnetic domain wall channel is proposed. By changing the offset angle between the magnetic moments on both sides of the magnetic domain wall and the channel direction, the transmission of spin waves in the channel can be allowed or suppressed, thereby designing a nanoscale three-terminal spin wave logic device.

[0006] Technical solution: In order to solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0007] A three-terminal nanoscale spin wave logic device based on a magnetic domain wall transmission mode is fabricated by changing the offset angle between the magnetic moments on both sides of the magnetic domain wall and the channel direction to allow or suppress the transmission of spin waves in the channel.

[0008] Furthermore, by coupling a pinned layer with in-plane magnetization under the magnetic waveguide film layer with perpendicular magnetic anisotropy, the magnetization orientation of the pinned layer is used to regulate the magnetic moment arrangement on both sides of the magnetic domain wall channel in the waveguide layer, thereby forming a T-type three-terminal spin wave device consisting of a transverse channel and a longitudinal channel.

[0009] Furthermore, by arranging wave excitation antennas at both ends of the transverse channel, the input of spin waves can be realized.

[0010] Furthermore, the transmission of spin waves in the longitudinal channel is achieved through the coherent excitation of spin waves in the transverse channel.

[0011] Furthermore, the longitudinal channel spin wave transmission is turned on and off by fine-tuning the direction of the magnetic moments at both ends of the longitudinal magnetic domain wall, thereby achieving the logical output of the spin wave.

[0012] Furthermore, through the in-plane magnetization pinning layer, the interlayer coupling effect is utilized to guide the magnetic moment of the waveguide layer to rearrange, thereby forming a magnetic domain wall between two magnetic domains with different magnetization orientations.

[0013] Furthermore, when the magnetization directions of adjacent reverse magnetization domains are arranged along the direction of the magnetic domain wall to form a Bloch-type domain wall, the magnetic moment in the domain wall is arranged along a plane perpendicular to the domain wall; when the magnetization directions of adjacent reverse magnetization domains form an offset angle θ with the domain wall, a transverse dipole field is formed in the domain wall, causing the Bloch-type domain wall to transition to a Néel-type domain wall.

[0014] Furthermore, sinusoidal time-harmonic excitation signals are input into the two antennas A1 and A2 of the transverse channel to drive the regular oscillation of the magnetic moment near the antenna. Under the exchange and dipole interaction between neighboring magnetic charges, the spin wave is propagated along the transverse magnetic domain wall, and the change of wave vector direction and the propagation of longitudinal spin wave are realized through coherent excitation at the center of the channel.

[0015] Beneficial effects: Compared with the prior art, the present invention has the following advantages:

[0016] (1) The present invention provides a three-terminal nanoscale spin wave logic device based on a magnetic domain wall transmission mode, which utilizes a pinning layer to regulate the magnetic moment arrangement in a waveguide film layer, thereby avoiding interference with surrounding devices due to the use of an external magnetic field.

[0017] (2) The present invention uses a magnetic film with out-of-plane perpendicular anisotropy as a waveguide, which greatly enhances the amplitude of the spin wave in the out-of-plane direction. Combined with the low scattering characteristics of the domain wall-type spin wave transmission channel, the long-distance transmission of the spin wave and the nanoscale of the wavelength are achieved, which provides ideas for the design of nanoscale spin wave devices.

[0018] (3) The present invention provides an excitation scheme based on coherent excitation, which enables spin waves to pass through sharp vertical paths, providing a feasible solution for designing highly integrated complex magnetic circuit devices.

[0019] (4) The present invention utilizes slight changes in the magnetic moment arrangement of the magnetic domains on both sides of the magnetic domain wall to regulate the strength of the transverse field in the magnetic domain wall, and in this way serves as a switch to control the transmission of spin waves in the output channel, thereby realizing the conversion of the output "AND" and "OR" logic gates in the three-terminal device. This control scheme realizes the control of logical output with extremely low energy consumption, providing ideas for the design of low-energy consumption devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic diagram of the structure of a three-terminal nanoscale spin wave logic device based on the magnetic domain wall transmission mode;

[0021] Figure 2 This is the distribution diagram of the relationship between the spin wave transmission intensity, transmission frequency and offset angle; (a) is the transverse domain wall channel, and (b) is the longitudinal domain wall channel.

[0022] Figure 3 It is the logic gate formed in the three-terminal device; (a) is the output of the "AND" gate; (b) is the output of the "OR" gate; (c) is the output of the "NOT" gate. DETAILED DESCRIPTION

[0023] The present invention is further illustrated below in conjunction with specific examples. The examples are implemented based on the technical solutions of the present invention. It should be understood that these examples are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0024] The present invention proposes a three-terminal spin wave logic device based on reconfigurable magnetic domain wall transmission. The scheme couples a pinned layer with in-plane magnetization under a magnetic waveguide film layer with perpendicular magnetic anisotropy, and uses the magnetization orientation of the pinned layer to regulate the magnetic moment arrangement on both sides of the magnetic domain wall channel in the waveguide layer, thereby forming a T-type three-terminal spin wave device consisting of transverse and longitudinal domain wall channels. The input of spin waves is realized by inserting wave excitation antennas at both ends of the transverse channel. The transmission of spin waves in the longitudinal channel is realized by coherent excitation of spin waves in the transverse channel. The on and off of the spin wave transmission in the longitudinal channel is realized by fine-tuning the direction of the magnetic moments at both ends of the longitudinal magnetic domain wall, thereby realizing the logic output of the spin wave.

[0025] This embodiment discloses a waveguide structure based on reconfigurable magnetic domain wall transmission spin wave, which is a "T"-shaped three-terminal device, composed of transverse and longitudinal nanowires with a length of 1500nm and a width of 200nm, and the angle between the transverse and longitudinal channels is 90°, such as Figure 1 (a) In addition, the waveguide structure is realized in a perpendicular magnetic anisotropy nano-ferromagnetic Co / Pt multilayer film material with the easy magnetization direction along the z-axis.

[0026] By replacing the external magnetic field with an in-plane magnetized pinned layer, the magnetic moment of the waveguide layer is rearranged through the interlayer coupling effect, thereby forming a magnetic domain wall between two magnetic domains with different magnetization orientations. When the magnetization directions of adjacent reverse magnetization domains are arranged along the direction of the magnetic domain wall to form a Bloch-type domain wall, the magnetic moments in the domain wall are arranged in a plane perpendicular to the domain wall. When the magnetization directions of adjacent reverse magnetization domains form a certain offset angle θ with the domain wall, a transverse dipole field will be formed in the domain wall, causing the Bloch-type domain wall to transition to a Néel-type domain wall.

[0027] The input of spin waves is realized by signal excitation antennas placed at both ends of the transverse channel, such as Figure 1 (b) Inputting sinusoidal time-harmonic excitation signals into the two antennas A1 and A2 can drive the regular oscillation of the magnetic moment near the antennas, and under the exchange and dipole interaction between neighboring magnetic charges, the spin wave propagates along the transverse (x-direction) magnetic domain wall, and the change of the wave vector direction and the longitudinal spin wave propagation are achieved through coherent excitation at the center of the channel.

[0028] Figure 1 (c) and (d) show the spin wave dispersion relations of DW propagating along the x and y directions. It can be seen that the spin waves along the transverse and longitudinal DW channels have significantly different characteristics in the wave dispersion relations. The propagation of spin waves in the transverse channel is mainly determined by the exchange dispersion relation, while the propagation of longitudinal spin waves originates from the coherent excitation of the interference and diffraction of transverse spin waves at the intersection. Unlike traditional electromagnetic waves, the wavelength λ of the spin waves generated by coherent excitation increases significantly without wave intensity enhancement. This shows that the phase velocity of the longitudinal spin wave is much greater than the phase velocity of the transverse channel.

[0029] The spin wave logic device design of the present invention is realized by micromagnetic simulation method. 3 The device model of the size is solved by the open source OOMMF software to solve the Landau-Lifshitz-Gilbert dynamic equation, which can obtain the observation of the dynamic process of magnetization reversal of the magnetic moment. To ensure the reliability of the simulation, the model discretization size is set to (3×3×2)nm 3 , which is much smaller than the exchange length between magnetic moments. The detailed parameters of the waveguide film layer are set as follows: anisotropy constant K u =0.8MJ / m 3 , the exchange constant A ex =25pJ / m, Dzyaloshinskii-Moriya (DM) interaction constant D =1mJ / m 2 , the saturation magnetization is M s =800 kA / m and damping coefficient α = 0.02. The device boundary adopts natural boundary conditions, and in order to suppress the spin wave reflection at the boundary, the damping coefficient of the boundary is set to α = 1.

[0030] In the spin wave device of the present invention, the intensity of the spin wave is mainly related to the transmission frequency and the deviation angle of the magnetic moments on both sides of the magnetic domain wall from the direction of the domain wall, such as Figure 2 (a) and (b). In the transverse domain wall channel, the spin wave is directly excited by the antenna, and the wave intensity tends to weaken with the increase of the excitation frequency, but a clear wave intensity signal can be obtained when the excitation frequency varies from 0.1 to 30 GHz. The increase of the offset angle will increase the transverse equivalent field in the domain wall region, so the increase of the angle will lead to a significant decrease in the wave intensity. And a frequency gap will be generated in the offset angle range of 5° to 15°. For the longitudinal domain wall channel, the spin wave is formed by the coherent excitation of the spin wave in the transverse channel. This process requires the minimum offset angle to be greater than 0. For the phase excitation of the A1 and A2 antennas, the required minimum offset angle is 14°. When the offset angle is greater than 16°, stable spin wave transmission can be obtained at 0.1 to 30 GHz, and the wave intensity weakens with the increase of the offset angle. For the spin wave excited by the single excitation source of the A1 or A2 antenna, the minimum offset angle required for longitudinal channel transmission is 20°, and the film layer needs to meet the assistance of DM interaction.

[0031] The spin wave device of the present invention can realize the output of logic gates "AND", "OR" and "NOT A", such as Figure 3As shown. The 1 (or 0) of the input signal is identified by the presence (or absence) of spin wave input in the transverse channel, and the 1 (or 0) of the output signal is identified by whether a spin wave is formed in the longitudinal output channel. By setting the domain wall offset angle of the longitudinal channel to 18° and the DM interaction constant to 1mJ / m 2 ,like Figure 3 As shown in (a), the device can be made to perform an AND gate operation, which obtains a signal output of 1 in the longitudinal channel only when the A1 and A2 antennas simultaneously input an excitation frequency of 10 GHz (the excitation frequency of 0.1 to 30 GHz can achieve signal input). By setting the domain wall offset angle of the longitudinal channel to 20° and the DM interaction constant to 1 mJ / m 2 ,like Figure 3 As shown in (b), the device can be made to perform an “OR” gate operation. If there is a signal input to any channel of the A1 or A2 antenna, the spin wave output of the longitudinal channel can be obtained. Based on the “OR” gate setting, the excitation frequency of the A1 antenna is adjusted to 40 GHz, and the input is set to 1 if there is a spin wave input. Figure 3 As shown in (c), the device can be made to perform “not A operation”. When input channel 1 is identified as 1, the spin wave output of the longitudinal channel will be suppressed.

[0032] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A three-terminal nanoscale spin wave logic device based on a magnetic domain wall transmission mode, characterized in that: By changing the offset angle between the magnetic moments on both sides of the magnetic domain wall and the channel direction, the transmission of spin waves in the channel can be allowed or suppressed, thus making a nanoscale three-terminal spin wave logic device.

2. The three-terminal nanoscale spin wave logic device based on the magnetic domain wall transmission mode according to claim 1, characterized in that: By coupling a pinned layer with in-plane magnetization under a magnetic waveguide film layer with perpendicular magnetic anisotropy, the magnetization orientation of the pinned layer is used to regulate the magnetic moment arrangement on both sides of the magnetic domain wall channel in the waveguide layer, forming a T-type three-terminal spin wave device consisting of a transverse channel and a longitudinal channel.

3. The three-terminal nanoscale spin wave logic device based on the magnetic domain wall transmission mode according to claim 2, characterized in that: The input of spin waves is achieved by setting wave excitation antennas at both ends of the transverse channel.

4. The three-terminal nanoscale spin wave logic device based on the magnetic domain wall transmission mode according to claim 2, characterized in that: The transmission of spin waves in the longitudinal channel is achieved through the coherent excitation of spin waves in the transverse channel.

5. The three-terminal nanoscale spin wave logic device based on the magnetic domain wall transmission mode according to claim 2, characterized in that: The longitudinal channel spin wave transmission is turned on and off by fine-tuning the direction of the magnetic moments at both ends of the longitudinal magnetic domain wall, thereby achieving the logical output of the spin wave.

6. The three-terminal nanoscale spin wave logic device based on the magnetic domain wall transmission mode according to claim 2, characterized in that: Through the in-plane magnetization pinning layer, the interlayer coupling effect is used to guide the magnetic moment of the waveguide layer to rearrange, thereby forming a magnetic domain wall between two magnetic domains with different magnetization orientations.

7. The three-terminal nanoscale spin wave logic device based on the magnetic domain wall transmission mode according to claim 6, characterized in that: When the magnetization directions of adjacent reverse magnetization domains are arranged along the direction of the magnetic domain wall to form a Bloch-type domain wall, the magnetic moment in the domain wall is arranged along a plane perpendicular to the domain wall; when the magnetization directions of adjacent reverse magnetization domains form an offset angle θ with the domain wall, a transverse dipole field is formed in the domain wall, causing the Bloch-type domain wall to transition to a Néel-type domain wall.

8. The three-terminal nanoscale spin wave logic device based on the magnetic domain wall transmission mode according to claim 2, characterized in that: Sinusoidal time-harmonic excitation signals are input into the two antennas A1 and A2 of the transverse channel to drive the regular oscillation of the magnetic moment near the antenna. Under the exchange and dipole interaction between neighboring magnetic charges, the spin wave propagates along the transverse magnetic domain wall, and the change of wave vector direction and the propagation of longitudinal spin wave are achieved through coherent excitation at the center of the channel.

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