Strain dependent magnetocrystalline anisotropy in metallic antiferromagnet Fe₂As from first principles

Magnetocrystalline anisotropy (MCA) is essential to understand spin dynamics and strain can be controlled in experiments to modify MCA. We used first-principles density functional theory to compute the strain dependence of MCA for Fe₂As, which has the same magnetic structure as the representative metallic antiferromagnet, CuMnAs, that exhibited potential for electrical switching.

We first calculated MCA without strain then tested uni-axial strains. The out-of-plane MCA as function of spin angle has 2-fold symmetry without strain, reaching up to a large amount of 600μeV. Symmetry was preserved with strain and out-of-plane MCA decreased linearly by 57μeV per 1% compressive strain. The in-plane MCA showed 4-fold symmetry without strain and magnitude 100 times smaller than out-of-plane, which signifies smaller magnetic field for spin switching. In-plane MCA symmetry was converted to 2-fold with strain, accompanied by 40 times higher MCA barrier with 0.1% strain.

Our study predicts that -5% strain can decrease out-of-plane MCA by half and in-plane MCA can be increased to be one order of magnitude larger than original value, reducing unfavorable spin fluctuations. This prediction provides an index to apply strain that can control MCA barrier for either easier spin switching or stabilized domains.