Abstract
In this work, we study the magnetic orders of a classical spin model with anisotropic exchanges and Dzyaloshinskii-Moriya interactions in order to understand the uniaxial stress effect in chiral magnets such as MnSi. Variational zero temperature calculations demonstrate that various helical orders can be developed depending on the interaction anisotropy magnitude, consistent with experimental observations at low temperatures. Furthermore, the uniaxial stress induced creation and annihilation of skyrmions can be also qualitatively reproduced in our Monte Carlo simulations. Our work suggests that the interaction anisotropy tuned by applied uniaxial stress may play an essential role in modulating the magnetic orders in strained chiral magnets.
Highlights
In the past years, the nontrivial magnetic orders observed in chiral magnets such as MnSi1–3, Fe1−xCoxSi4 and FeGe5, 6 have been attracting continuous attention due to the interesting physics and potential applications for future memory technology
Some spin models were proposed and the ordered phases found in experiments on bulk MnSi have been successfully reproduced, allowing one to explore the stress effect based on such models[12]
We study the classical Heisenberg spin model including anisotropic FM exchange and DM interactions on a three-dimensional lattice by combining variational zero-T calculations with Monte Carlo (MC) simulations to understand the stress induced magnetic orders in bulk MnSi
Summary
The classical Heisenberg spin model taking account of the DM interaction and anisotropic exchange applicable to strained MnSi is considered and its Hamiltonian is given by:. In the isotropic bulk system under zero h, the ground state is a helical order with wave vector[8] k = arctan(D/ 3 J) (1, 1, 1) and its orientation is usually related to the weak magneto-crystalline anisotropy[34, 35]. An exact solution of the model further considering the magneto-crystalline anisotropy is hard to access using the variational method. Such an anisotropy is not considered here in order to help one to understand the effect of interaction anisotropy, and our physical conclusions are not affected by this ignorance. By optimizing for k and (θ, φ), we obtain the following set of equations: Jx tan kx Jy tan ky
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