A spin wave diode based on an artificial antiferromagnetic structure

Abstract

The present invention provides a spin wave diode based on an artificial antiferromagnetic structure, comprising: an artificial antiferromagnetic structure, comprising a first ferromagnetic material layer, a nano-insulating layer, a second ferromagnetic material layer and a heavy metal layer arranged in sequence from top to bottom, wherein both ends of the second ferromagnetic material layer are not covered by the first ferromagnetic material layer and the nano-insulating layer; a first integrated coplanar waveguide and a second integrated coplanar waveguide, respectively located on the left upper surface and the right upper surface of the second ferromagnetic material layer, wherein one of the first integrated coplanar waveguide and the second integrated coplanar waveguide is used to excite a spin wave, and the other is used to detect the spin wave. The present invention can accurately control the transmission characteristics of the spin wave by regulating the relative orientation of the interlayer magnetic moment and the DM constant, thereby achieving unidirectional transmission performance.

Description

Technical Field

[0001] The present invention belongs to but is not limited to the technical field of magnetic materials and spin electronics, and in particular relates to a spin wave diode based on an artificial antiferromagnetic structure. Background Art

[0002] As an emerging technology, spin electronics is an important field after modern electronics and optoelectronics. Unlike traditional electronics that rely on electron charge, spin waves use electron spin and magnetic moment to transmit and store information. Spin waves are excited states of magnetism in magnetic materials. They have both the advantages of waves and particle characteristics and can be used for logic calculations, reservoir calculations, etc. The transmission of spin waves is based on the exchange of angular momentum and does not require the movement of electrons. Therefore, the transmission loss is small and the Joule heat generated is negligible. 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 semiconductor processes.

[0003] One of the keys to realizing a spin-wave-based chip architecture is to realize a spin-wave diode. The methods that have been proposed include a domain-wall-based spin-wave diode, which uses a chiral Née wall or Bloch wall as a spin-wave waveguide. The chirality of the domain wall or the non-reciprocity caused by the dipole effect realizes the unidirectional transmission of spin waves; or the unidirectional transmission of spin waves is realized through complex structural design. Most of these methods are complex in structure and difficult to implement. For example, spin-wave domain wall waveguides are difficult to accurately prepare through micro-nano processing; and the working bandwidth is narrow, mostly operating at several GHz. In response to this, we propose a spin-wave diode based on artificial antiferromagnetism. Artificial antiferromagnetism has a simple structure and commercial products. It is easy to prepare and has a greatly improved working bandwidth of up to tens of GHz. Summary of the invention

[0004] In view of the problems existing in the prior art, the present invention provides a spin wave diode based on an artificial antiferromagnetic structure. The spin wave diode based on the artificial antiferromagnetic structure is characterized in that the spin wave diode based on the artificial antiferromagnetic structure is a four-layer artificial antiferromagnetic structure composed of two layers of ferromagnetic materials (FM), a middle layer of nano insulating layer and a bottom heavy metal layer Pt, and the diode device includes integrated coplanar waveguides (CPW) CPW1 and CPW2 for exciting and receiving spin waves, and the protruding parts at both ends serve as the excitation end and the receiving end of the spin wave.

[0005] Furthermore, the length of the top layer is set to 3000nm, the bottom layer including the excitation end and the receiving end is set to 3300nm in length, the width is 80nm, the thickness d is set to 0.6nm, and the black long strips CPW1 and CPW2 at both ends of the model serve as spin wave excitation and detection devices.

[0006] Furthermore, the diode structure excites spin waves by applying microwave signals, and CPW1 excites CPW2 to detect spin waves, or CPW2 excites CPW1 to detect spin waves.

[0007] Due to the interlayer dipole effect in the artificial antiferromagnetic layer and the DM (Dzyaloshinskii-Moriya) effect in the FM2 layer, the spin wave is non-reciprocally transmitted in the FM2 layer, and unidirectional transmission occurs in a specific frequency band, and the difference in the spin wave amplitude in the opposite direction is more than two orders of magnitude. The non-reciprocity of spin wave transmission can be further controlled by applying an external magnetic field.

[0008] When the DM action constant D is 2mJ / m 2 When the interlayer magnetic moments are antiparallel, the study found that when the spin wave frequency is between 30GHz and 45GHz, the spin wave exhibits a unidirectional transmission characteristic in the -x direction; when D is changed to -2mJ / m 2 Yes, the spin wave is transmitted unidirectionally along the +x direction. When the magnetic moments between the layers are parallel, the spin wave is transmitted bidirectionally. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0010] Figure 1 is a schematic structural diagram of a spin wave diode based on an artificial antiferromagnetic structure provided by an embodiment of the present invention;

[0011] Figure 2 is a dispersion diagram of spin wave transmission in the FM2 magnetic layer of a spin wave diode based on an artificial antiferromagnetic structure provided by an embodiment of the present invention;

[0012] Figure 3 It is the transmission state of the spin wave of the spin wave diode based on the artificial antiferromagnetic structure provided by the embodiment of the present invention in the FM2 layer when t=5ns, and the spin wave frequency is 30GHz;

[0013] Figure 4 The spin wave diode based on the artificial antiferromagnetic structure provided by the embodiment of the present invention has a DM action constant D of 2mJ / m 2 and -2mJ / m 2 Transmission mode diagram of spin waves in the FM2 layer when the spin wave frequency is 30 GHz. DETAILED DESCRIPTION

[0014] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0015] Combine the following Figure 1 The present invention describes a diode based on the unidirectional transmission characteristic of spin waves, comprising:

[0016] The embodiment of the present invention provides a spin wave diode based on an artificial antiferromagnetic structure, which is an artificial antiferromagnetic structure with a four-layer structure consisting of two FM layers of ferromagnetic materials, a middle nano-insulating layer and a bottom heavy metal layer Pt. The FM layer is generally selected from CoFeB, and the insulating layer is generally selected from MgO, and other materials can also be used. The diode device includes integrated coplanar waveguides CPW1 and CPW2 for exciting and receiving spin waves, and the protruding parts at both ends serve as the excitation end and the receiving end of the spin wave. The coplanar waveguide is used to excite and detect the spin wave, and CPW1 excites CPW2 to detect the spin wave, or CPW2 excites CPW1 to detect the spin wave.

[0017] The length of the top layer is set to 3000nm, the length of the bottom layer including the excitation end and the receiving end is set to 3300nm, the width is 80nm, and the thickness d is set to 0.6nm. The black strips CPW1 and CPW2 at both ends of the model serve as the excitation and detection devices of the spin wave.

[0018] Due to the interlayer dipole effect in the artificial antiferromagnetic layer and the DM effect in the FM2 layer, the spin wave is non-reciprocally transmitted in the FM2 layer, and unidirectionally transmitted in a specific frequency band. The difference in the spin wave amplitude in the opposite direction is more than two orders of magnitude, such as Figure 2 By applying an external magnetic field, the non-reciprocity of spin wave transmission can be further controlled and the unidirectional transmission characteristics of spin waves can be enhanced.

[0019] This paper mainly studies the unidirectional transmission of spin waves in the bottom magnetic layer FM2, and the DM action constant D is 2mJ / m 2 , saturation magnetization M s When the damping coefficient α is 680kA / m and 0.01, the simulation shows that when the transmission frequency of the spin wave is between 30GHz and 45GHz, the spin wave transmission shows obvious unidirectional transmission characteristics in the -x direction. The spin wave is excited by applying an excitation at the middle position of the FM2 layer of the model at a frequency of 30GHz. The transmission process of the spin wave at a certain moment is as follows: Figure 3As shown, it can be clearly seen that the spin wave is transmitted unidirectionally along the -x direction, and the spin wave amplitudes in the +x direction and the -x direction differ by more than 2 orders of magnitude.

[0020] By changing the positive or negative value of the DM action constant, the dispersion curve changes symmetrically, and the spin wave changes from unidirectional transmission in the -x direction to unidirectional transmission in the +x direction. Therefore, we can control the direction of unidirectional transmission of the spin wave by adjusting the positive or negative value of D.

[0021] When D>0, the spin wave is transmitted unidirectionally along the -x direction, so the spin wave can only be excited by the CPW2 port and received by the CPW1 port; when D<0, the spin wave is transmitted unidirectionally along the +x direction, so the spin wave can only be excited by the CPW1 port and received by the CPW2 port; thus, the conduction and cutoff of the spin wave diode are realized. When D is 2mJ / m 2 and -2mJ / m 2 When the spin waves are excited at the left and right ends, the transmission mode is shown in the figure Figure 4 As shown, the structure has the unidirectional conduction characteristic of spin waves and is a typical spin wave diode.

[0022] 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 it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A spin wave diode based on an artificial antiferromagnetic structure, characterized in that: The diode is an artificial antiferromagnetic structure with a four-layer structure consisting of two ferromagnetic material layers FM1 and FM2, a nano-insulating layer between FM1 and FM2, and a heavy metal layer at the bottom. The diode includes integrated coplanar waveguides CPW1 and CPW2 for exciting and receiving spin waves. The protruding parts at both ends of the artificial antiferromagnetic structure serve as the excitation end and the receiving end of the spin wave. The top ferromagnetic material layer and nano-insulating layer are 3000 nm long, and the bottom ferromagnetic material layer and heavy metal layer are 3300 nm long, forming two protruding ends. Each layer in the four-layer structure is 80 nm wide and has a thickness d of 0.6 nm. The strip-shaped CPW1 and CPW2 located on the upper surface of the two protruding ends serve as spin wave excitation and detection devices. The diode excites a spin wave through a coplanar waveguide, and the FM2 layer serves as a spin wave transmission layer. CPW1 excites CPW2 to detect the spin wave, or CPW2 excites CPW1 to detect the spin wave.

2. The spin wave diode based on artificial antiferromagnetic structure according to claim 1, characterized in that: Due to the interlayer dipole effect in the artificial antiferromagnetic structure and the DM effect in the FM2 layer, spin waves exhibit non-reciprocal transmission in the FM2 layer and unidirectional transmission in a specific frequency band. The difference in spin wave amplitudes in opposite directions is more than two orders of magnitude. By applying an external magnetic field, the non-reciprocity of spin wave transmission can be further controlled.

3. The spin wave diode based on artificial antiferromagnetic structure according to claim 1, characterized in that: The interlayer magnetic moments are arranged antiparallel. When the DM action constant D>0, the spin wave is transmitted unidirectionally along the -x direction; when D<0, the spin wave is transmitted unidirectionally along the +x direction.

4. The spin wave diode based on an artificial antiferromagnetic structure according to claim 1, characterized in that: The FM1 is CoFeB, the nano insulating layer is MgO, the FM2 is CoFeB, and the heavy metal layer is Pt.

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