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Quantum mechanics simulation method for magnetic skyrmion lattices and magnetic vortex lattices

A technology of skyrmion lattice and quantum mechanics, which is applied in the field of quantum mechanical simulation of magnetic skyrmion lattice and magnetic vortex lattice, can solve the problem of inability to simulate antiferromagnetic skyrmion lattice, Monte-Carlo Lo is not ideal, the micromagnetic description is no longer accurate and reliable, etc.

Active Publication Date: 2019-12-06
刘照森
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  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

Because micromagnetism is based on the continuum model, it can still describe large-scale skyrmions, but in this tiny scale, the continuum model is no longer applicable, so the description of micromagnetism is no longer accurate and reliable[21]
On the other hand, due to the significant quantum effects on the microscopic scale, Monte Carlo also becomes unsatisfactory. For example, it cannot simulate the antiferromagnetic skyrmion lattice on the square lattice[8]

Method used

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  • Quantum mechanics simulation method for magnetic skyrmion lattices and magnetic vortex lattices
  • Quantum mechanics simulation method for magnetic skyrmion lattices and magnetic vortex lattices
  • Quantum mechanics simulation method for magnetic skyrmion lattices and magnetic vortex lattices

Examples

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Embodiment 1

[0092] Embodiment 1: Ferromagnetic Skymion Crystal of Bloch-Type Ferromagnetic Skymion Crystal of Bloch-Type

[0093] A 30×30 square grid is used in the simulation, and there is a spin of S=1 on each grid point. In order to simulate infinite two-dimensional systems with it, periodic boundary conditions are adopted. The effect of perpendicular anisotropy is not considered here, and J=1K is set, and D / J=1.02733, so that the periodic distance between skyrmions λ=10.

[0094] It can be seen from the simulation results that in the absence of an external field, the spontaneous ground state of this two-dimensional system is a strip structure along the [110] direction; gradually increasing the vertical external magnetic field When 0.11Tesla≤B≤0.27Tesla, a skyrmion lattice with a regular hexagonal close-packed structure will be produced in a square lattice; in a weak magnetic field, the space period of this array is 10, which is consistent with the theory; In the magnetic fie...

Embodiment 2

[0097] Embodiment 2: Bloch-type antiferromagnetic skyrmion array (Antiferromagnetic Skymion Crystalof Bloch-Type)

[0098] For this example, we study the antiferromagnetic situation, so take J=-1K, D=1K (so D / J=-1), K A = 0[8]. A 56×56 square grid is adopted, and there is a 5=1 spin on each grid point. Use periodic boundary conditions to simulate infinite two-dimensional systems. In the simulation, it was found that when the vertical applied magnetic field intensity satisfies 3.9Tesla≤B≤4.1Tesla, the antiferromagnetic skyrmion array can be formed in the temperature range of T / J<1.6; slightly increasing or weakening the applied magnetic field, antiferromagnetic The magnetic skyrmion lattice disappears and is replaced by an antiferromagnetic structure.

[0099] Figure II (b) shows the simulated antiferromagnetic skyrmion lattice at B=4Tesla, T / J=0.1. It has perfect symmetry with a space period λ=7. The average value of the z component of the spin in each skyrmion c...

example 1

[0100] B in Example 1 1 =0.11Tesla, B in Example 2 2 =4Tesla, and the ratio of D / J of the two is similar, but B2 / B1≈36.4. Therefore, to observe an array of antiferromagnetic skyrmions, a 36 times stronger magnetic field needs to be applied. In addition, the antiferromagnetic skyrmion lattice only exists in a narrow B interval, so it lacks good stability. All of these make experimental observations much more difficult.

[0101] It is necessary to point out that in order to simulate the antiferromagnetic skyrmions on the square lattice, R. Keesman et al. set J=-1, D / |J|=1, H / |J|=4, only in the 8×8 A single skyrmion can be simulated on a square lattice of finite size, but an antiferromagnetic skyrmion lattice on an infinite square system cannot be simulated [8]. However, the theoretical research by Tretiakov et al. showed that such skyrmions exist at non-zero temperatures and are more stable in an external magnetic field[23]. Therefore, this example illustrates the sig...

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Abstract

The invention relates to the field of computational physics and materials science, and applies quantum theory to simulation of magnetic skyrmion lattices and magnetic vortex lattices. The method comprises the steps that: 1, respective rotations in the Hamiltonian quantity of the magnetic system are quantum mechanics operators; 2, all physical quantities are calculated strictly according to a quantum theory; 3, a self-consistent algorithm is adopted; 4, simulation is performed on gradual reduction to low temperature from high temperature so as to ensure correct convergence of a program; 5, periodic boundary conditions are adopted; 6, a vertical external magnetic field is considered, so that spiral stripes generated by the exchange effect of the DMI and the Heisenberg are changed into skyrmion or vortex lattices; 7, when Heisenberg exchange and DMI effects coexist, the Compass type anisotropy effect is considered, and skyrmion lattices with the opposite neighbor vortex directions are simulated. The defects of micro-magnetism and a Monte-Carlo two-classic method are overcome, so that simulation is very flexible and convenient, and particularly in a quantum scale, a periodic magnetic structure which cannot be calculated by the two-classic method is simulated.

Description

technical field [0001] The invention belongs to the fields of computational physics and computational materials science, and in particular relates to a quantum mechanical simulation method of a magnetic skyrmion lattice and a magnetic vortex lattice. Because the size of magnetic skyrmions and magnetic vortices is often on the nanometer scale, and the current that needs to be manipulated is very small, they are regarded as ideal candidates for the next generation of magnetic storage and magnetic logic operations, and thus have important theoretical and Value. Background technique [0002] For decades, researchers at home and abroad have widely used two numerical methods, Monte Carlo [1] and Micromagnetics [2, 3], to simulate the microscopic magnetic structure of magnetic materials and to study their macroscopic physical properties. . The achievements of these two methods in scientific research and their status in computational physics are universally recognized. There are c...

Claims

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Application Information

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IPC IPC(8): G06F17/50
CPCY02E60/00
Inventor 刘照森
Owner 刘照森
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