Method for regulating and controlling spin state of two-dimensional antiferromagnetic semiconductor by using JANUS structure

Abstract

The invention discloses a method for regulating and controlling the spin state of a two-dimensional antiferromagnetic semiconductor by using a JANUS structure, and the method comprises the following steps: constructing a two-dimensional antiferromagnetic semiconductor material structure model, and carrying out the geometric optimization; calculating magnetic properties and electronic properties based on the optimized structure; replacing halogen atoms on one side to obtain a two-dimensional A-type antiferromagnetic semiconductor material structure model with a JANUS structure, and performing geometric optimization; based on the optimized JANUS structure, the magnetic property and the electronic property of the JANUS structure are calculated; and comparing the spin state near the Fermi level of the optimized two-dimensional antiferromagnetic semiconductor material with the spin state near the Fermi level of the optimized two-dimensional A-type antiferromagnetic semiconductor material with the JANUS structure. According to the method, on the basis of a two-dimensional antiferromagnetic material, a JANUS structure is introduced, the magnetism of the material is not changed, meanwhile, a single polarization spin electron current is introduced at the Fermi level, and a theoretical model is provided for preparing related materials.

Description

Technical Field

[0001] The invention belongs to the technical field of spin regulation of two-dimensional antiferromagnetic semiconductor materials, and specifically relates to a method for regulating the spin state of a two-dimensional antiferromagnetic semiconductor by using a JANUS structure. Background Art

[0002] Two-dimensional magnetic semiconductors integrate both magnetic and semiconductor properties at the atomic scale, are compatible with the current semiconductor industry, and are an important technology for nano-spin electronic devices. Two-dimensional antiferromagnetic semiconductor materials are a special type of magnetic material with unique magnetic and electrical properties. Therefore, they have broad application prospects in magnetic storage, spin electronics, quantum computing and other fields. In two-dimensional antiferromagnetic semiconductor materials, the magnetic moments of adjacent atoms are arranged in opposite directions and are equal in size, so the net magnetic moment is zero, thereby eliminating the influence of external stray magnetic fields and improving the integration of devices. At the same time, two-dimensional antiferromagnetic semiconductor materials generally have a higher magnetic transition temperature and are not affected by magnetic domain walls. They are ideal materials for spin-polarized scanning tunneling microscope probes, spin valves and single-spin superconductors.

[0003] However, due to the degeneracy of spin electron energy levels in two-dimensional antiferromagnetic semiconductor materials, the local magnetic moments cancel each other out and single spin-polarized carriers cannot be obtained, which limits their application in spin electronic devices. Current methods for inducing spin-polarized carriers in two-dimensional antiferromagnetic semiconductor materials usually include doping semiconductors with dilute magnetic metal atoms, substituting elements in ordered double perovskite materials, designing binary Heusler alloys, introducing vacancies in Mott insulators, using single-layer superlattice structures, and doping carriers in perovskite cuprates.

[0004] The above methods can break the spin degeneracy in two-dimensional antiferromagnetic semiconductor materials, making the materials exhibit antiferromagnetic half-metal or asymmetric antiferromagnetic semiconductor behavior. However, the above methods are usually affected by lattice distortion, surface properties and temperature effects, and are difficult to achieve effective control experimentally. Summary of the invention

[0005] The purpose of the present invention is to provide a method for regulating the spin state of a two-dimensional antiferromagnetic semiconductor using a JANUS structure, so as to solve the problem that the prior art is usually affected by lattice distortion, surface properties and temperature effects, and is difficult to achieve effective control in experiments.

[0006] The technical solution adopted by the present invention is a method for regulating the spin state of a two-dimensional antiferromagnetic semiconductor using a JANUS structure, and the specific steps are as follows:

[0007] S1: Construct a structural model of two-dimensional antiferromagnetic semiconductor materials, perform geometric optimization on the structural model of two-dimensional antiferromagnetic semiconductor materials, and obtain a structure with the lowest total atomic internal energy;

[0008] S2: Based on the optimized structure, calculate the magnetic and electronic properties of two-dimensional antiferromagnetic semiconductor materials;

[0009] S3: Replace the halogen atoms on one side to obtain the structural model of a two-dimensional A-type antiferromagnetic semiconductor material with a JANUS structure, and perform geometric optimization on it;

[0010] S4: Based on the optimized JANUS structure, the magnetic and electronic properties of two-dimensional A-type antiferromagnetic semiconductor materials are calculated;

[0011] S5: Compare the spin states near the Fermi level of the two-dimensional antiferromagnetic semiconductor material optimized in S2 and the two-dimensional A-type antiferromagnetic semiconductor material with JANUS structure optimized in S4.

[0012] The present invention is also characterized in that:

[0013] The structural model of the two-dimensional antiferromagnetic semiconductor material constructed in S1 is MX type or Mxene type, and the structural model of the A-type two-dimensional antiferromagnetic semiconductor material with JUNAS structural characteristics in S3 is MX type or Mxene type;

[0014] In S1, a first-principles quantum mechanics simulation software based on density functional theory is used to establish a structural model of two-dimensional antiferromagnetic semiconductor materials;

[0015] In S1, a conjugate gradient algorithm or a quasi-Newton algorithm is used to optimize the geometric structure of the structural model of the two-dimensional antiferromagnetic semiconductor material to obtain a model with the lowest total internal energy;

[0016] The specific method for calculating the magnetic and electronic properties in S2 and S4 is: using the hybrid functional method, determine the magnetic ground state of the material based on the minimum energy principle. After determining the magnetic ground state, analyze the conductivity of the material and the spin state near the Fermi level from the energy band diagram, use the energy mapping method to obtain the strength of the exchange interaction between the spin centers, and use the Monte Carlo method to determine the magnetic transition temperature.

[0017] In S3, the conjugate gradient algorithm or quasi-Newton algorithm is used to perform geometric optimization on two-dimensional A-type antiferromagnetic semiconductor materials with JANUS structural characteristics.

[0018] The beneficial effects of the present invention are:

[0019] 1. The method of the present invention is based on MX-type and Mxene-type two-dimensional antiferromagnetic materials. By introducing the JANUS structure, a single polarized spin electron flow is introduced at the Fermi level without changing the magnetic properties of the two-dimensional antiferromagnetic material. The calculation method based on the first principle is simple to operate, highly accurate, widely used and has good repeatability.

[0020] 2. The method of the present invention constructs MX-type and Mxene-type two-dimensional antiferromagnetic materials with a JANUS structure, providing a theoretical model for the preparation of related materials and devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 : is a structural model diagram of MnCl in an embodiment of the present invention;

[0022] Figure 2 It is a structural model diagram of Cr2CF2 in an embodiment of the present invention;

[0023] Figure 3 is an energy band structure diagram of MnCl in an embodiment of the present invention;

[0024] Figure 4 is an energy band structure diagram of Cr2CF2 in an embodiment of the present invention;

[0025] Figure 5 Schematic diagram of the structural model of Mn2FCl in an embodiment of the present invention;

[0026] Figure 6 Schematic diagram of the structural model of Mn2ClBr in an embodiment of the present invention;

[0027] Figure 7 Schematic diagram of the structural model of Mn2ClI in an embodiment of the present invention;

[0028] Figure 8 Schematic diagram of the structural model of Cr2CFCl in an embodiment of the present invention;

[0029] Fig. 9 Schematic diagram of the structural model of Cr2CFBr in an embodiment of the present invention;

[0030] Fig.10 Schematic diagram of the structural model of Cr2CFI in an embodiment of the present invention;

[0031] Fig.11 is an energy band structure diagram of Mn2FCl in an embodiment of the present invention;

[0032] Fig.12 is an energy band structure diagram of Mn2ClBr in an embodiment of the present invention;

[0033] Fig.13 is an energy band structure diagram of Mn2ClI in an embodiment of the present invention;

[0034] Fig.14 is an energy band structure diagram of Cr2CFCl in an embodiment of the present invention;

[0035] Fig.15 is an energy band structure diagram of Cr2CFBr in an embodiment of the present invention;

[0036] Fig.16 is the energy band structure diagram of Cr2CFI in an embodiment of the present invention. DETAILED DESCRIPTION

[0037] The present invention is described in detail below in conjunction with specific implementation modes.

[0038] Example 1

[0039] The method of using the JANUS structure to control the spin state of a two-dimensional antiferromagnetic semiconductor is as follows:

[0040] S1: Construct a structural model of a two-dimensional antiferromagnetic semiconductor material such as MX or Mxene, specifically: use a first-principle quantum mechanics simulation software based on density functional theory to establish a structural model of a two-dimensional antiferromagnetic semiconductor material such as MX or Mxene;

[0041] Use the conjugate gradient algorithm or quasi-Newton algorithm to geometrically optimize the structural model of the two-dimensional antiferromagnetic semiconductor material of MX or Mxene to obtain the structure with the lowest total atomic internal energy;

[0042] S2: Based on the optimized structure, the magnetic and electronic properties of MX or Mxene two-dimensional antiferromagnetic semiconductor materials are calculated. Specifically, the hybrid functional method is used to determine the magnetic ground state of the material based on the minimum energy principle. After the magnetic ground state is determined, the conductivity of the material and the spin state near the Fermi level are analyzed by the energy band diagram. The strength of the exchange interaction between the spin centers is obtained by the energy mapping method, and the magnetic transition temperature is determined by the Monte Carlo method.

[0043] S3: Replace the halogen atoms on one side to obtain the structural model of the two-dimensional A-type antiferromagnetic semiconductor material of MX or Mxene with JANUS structural characteristics;

[0044] Use the conjugate gradient algorithm or quasi-Newton algorithm to perform geometric optimization on the structural model of two-dimensional A-type antiferromagnetic semiconductor materials with JANUS structural characteristics;

[0045] S4: Based on the optimized JANUS structure, the magnetic and electronic properties of two-dimensional A-type antiferromagnetic semiconductor materials are calculated. The specific method is as follows:

[0046] The hybrid functional method is used to determine the magnetic ground state of the material based on the principle of minimum energy. After the magnetic ground state is determined, the conductivity of the material and the spin state near the Fermi level are analyzed by the energy band diagram. The energy mapping method is used to obtain the strength of the exchange interaction between spin centers, and the Monte Carlo method is used to determine the magnetic transition temperature.

[0047] S5: Based on the above results, the spin states near the Fermi level of the two-dimensional antiferromagnetic semiconductor material optimized in S2 and the two-dimensional A-type antiferromagnetic semiconductor material with JANUS structure optimized in S4 are compared to determine whether the spin state near the Fermi level of the two-dimensional A-type antiferromagnetic semiconductor material with JUNAS structure has changed from a degenerate state to a single spin state, which is beneficial to obtain single spin polarized carriers and promote its application in spin electronic devices.

[0048] Example 2

[0049] Step 1: Take MnCl and Cr2CF2 as an example to construct Figure 1 , Figure 2 Atomic structure model shown;

[0050] Step 2: Use the conjugate gradient norm algorithm to fully relax the initial model to obtain a geometric structure with low total internal energy. In this step, the K point is set to 12×12×1, the cutoff energy is 500 eV, and the convergence criteria of energy and force are 0.01 eV and 10 respectively. -6 eV;

[0051] Step 3: Based on step 2, calculate the energy of different magnetic configurations of MnCl and Cr2CF2 respectively, find the magnetic ground state, and calculate the electronic structure energy band diagram of the material based on the structure of the magnetic ground state. The electronic structure energy band diagram of MnCl and Cr2CF2 is as follows: Figure 3 , Figure 4 As shown;

[0052] Table 1 Magnetic properties of MnCl and Cr2CF2

[0053]

[0054] Step 4: Based on the optimized structural model, the halogen atoms on one side are replaced so that the two sides have different halogen atoms, thereby obtaining a two-dimensional antiferromagnetic semiconductor material model of M2X1X2 (X1, X2 = F, Cl, Br, I and X1 is different from X2) or Mxene with JANUS structural characteristics, such as Figures 5 to 10 As shown;

[0055] Step 5: Based on step 4, the conjugate gradient algorithm is used to perform geometry optimization on the two-dimensional A-type antiferromagnetic semiconductor material with JANUS structure characteristics. In this step, the K point is set to 12×12×1, the cutoff energy is 500eV, and the convergence criteria of energy and force are 0.01eV and 10 respectively. -6 eV;

[0056] Step 6: Based on step 5, calculate the magnetic ground state of the two-dimensional A-type antiferromagnetic semiconductor material with JANUS structural characteristics. Calculate the electronic structure band diagram based on the magnetic ground state. The electronic structure band diagram is as follows: Figures 11 to 16 shown.

[0057] Table 2 Magnetic properties of JUNAS structure

[0058]

[0059]

[0060] Example 3

[0061] The method of using the JANUS structure to control the spin state of a two-dimensional antiferromagnetic semiconductor is as follows:

[0062] S1: Construct a structural model of two-dimensional antiferromagnetic semiconductor materials, perform geometric optimization on the structural model of two-dimensional antiferromagnetic semiconductor materials, and obtain a structure with the lowest total atomic internal energy;

[0063] S2: Based on the optimized structure, calculate the magnetic and electronic properties of two-dimensional antiferromagnetic semiconductor materials;

[0064] S3: Replace the halogen atoms on one side to obtain the structural model of a two-dimensional A-type antiferromagnetic semiconductor material with a JANUS structure, and perform geometric optimization on it;

[0065] S4: Based on the optimized JANUS structure, the magnetic and electronic properties of two-dimensional A-type antiferromagnetic semiconductor materials are calculated;

[0066] S5: Compare the spin states near the Fermi level of the two-dimensional antiferromagnetic semiconductor material optimized in S2 and the two-dimensional A-type antiferromagnetic semiconductor material with JANUS structure optimized in S4.

Claims

1. A method for controlling the spin state of a two-dimensional antiferromagnetic semiconductor using a JANUS structure, characterized in that: The specific steps are as follows: S1: Construct a structural model of two-dimensional antiferromagnetic semiconductor materials, perform geometric optimization on the structural model of two-dimensional antiferromagnetic semiconductor materials, and obtain a structure with the lowest total atomic internal energy; S2: Based on the optimized structure, calculate the magnetic and electronic properties of two-dimensional antiferromagnetic semiconductor materials; S3: Replace the halogen atoms on one side to obtain the structural model of a two-dimensional A-type antiferromagnetic semiconductor material with a JANUS structure, and perform geometric optimization on it; S4: Based on the optimized JANUS structure, the magnetic properties and electronic properties of the two-dimensional A-type antiferromagnetic semiconductor material are calculated; S5: Compare the spin states near the Fermi level of the two-dimensional antiferromagnetic semiconductor material optimized in S2 and the two-dimensional A-type antiferromagnetic semiconductor material with a JANUS structure optimized in S4.

2. The method for controlling the spin state of a two-dimensional antiferromagnetic semiconductor using a JANUS structure according to claim 1, characterized in that: The structural model of the two-dimensional antiferromagnetic semiconductor material constructed in S1 is MX type or Mxene type, and the structural model of the A-type two-dimensional antiferromagnetic semiconductor material with JUNAS structural characteristics in S3 is MX type or Mxene type.

3. The method for controlling the spin state of a two-dimensional antiferromagnetic semiconductor using a JANUS structure according to claim 1, characterized in that: In S1, a first-principles quantum mechanics simulation software based on density functional theory is used to establish a structural model of a two-dimensional antiferromagnetic semiconductor material.

4. The method for controlling the spin state of a two-dimensional antiferromagnetic semiconductor using a JANUS structure according to claim 1, characterized in that: In S1, a conjugate gradient algorithm or a quasi-Newton algorithm is used to optimize the geometric structure of the structural model of the two-dimensional antiferromagnetic semiconductor material to obtain a model with the lowest total internal energy.

5. The method for controlling the spin state of a two-dimensional antiferromagnetic semiconductor using a JANUS structure according to claim 1, characterized in that: The specific method for calculating the magnetic properties and electronic properties in S2 and S4 is: using the hybrid functional method to determine the magnetic ground state of the material based on the minimum energy principle, after determining the magnetic ground state, analyzing the conductivity of the material and the spin state near the Fermi level from the energy band diagram, using the energy mapping method to obtain the strength of the exchange interaction between the spin centers, and using the Monte Carlo method to determine the magnetic transition temperature.

6. The method for controlling the spin state of a two-dimensional antiferromagnetic semiconductor using a JANUS structure according to claim 1, characterized in that: In S3, a conjugate gradient algorithm or a quasi-Newton algorithm is used to perform geometric optimization on the two-dimensional A-type antiferromagnetic semiconductor material having JANUS structural characteristics.

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