Strain effect on magnetocrystalline anisotropy of Fe₂As from first principles

There has been emerging interest in metallic antiferromagnets since the potential for electrical switching was shown for CuMnAs and Mn₂Au. Magnetocrystalline anisotropy (MCA) is essential to understand spin dynamics and spin switching, and strain can be utilized to modify the anisotropy energy. We used first-principles density functional theory to compute the strain dependence of MCA for Fe₂As, which has the same magnetic structure as CuMnAs.

Without strain, out-of-plane MCA reached up to 600μeV and in-plane was 100 times smaller. Small in-plane MCA facilitates spin switching by requiring less magnetic field in experiments. We then tested uni-axially strained structures with strains picked between -1% and 1%. The out-of-plane MCA as function of spin angle showed 2-fold symmetry with and without strain. We extract a linear relationship between MCA and strain, leading to an increase of MCA by about 57μeV per 1% tensile strain.

This linearity can predict amount of compressive strain to lower the magnetic domain switching energy barrier. To reduce out-of-plane energy barrier by half, -5% strain is estimated. Further investigation in in-plane MCA would enable stabilization of domain switching in experiments by increasing the energy barrier with strain.