Spin-flop phase transition in the orthorhombic antiferromagnetic topological semimetal Cu0.95MnAs

TL;DR

This study investigates the magnetic anisotropy and phase transitions in CuMnAs compounds, revealing a spin-flop transition in Cu0.95MnAs and highlighting the effects of Cu vacancies on magnetic behavior.

Contribution

It provides detailed magnetic property analysis of CuMnAs compounds, discovering a spin-flop transition and the influence of Cu vacancies on magnetic interactions.

Findings

Cu0.95MnAs exhibits a spin-flop phase transition at high temperatures and low fields.

The b axis is the magnetic easy axis in Cu0.95MnAs, with the c axis as the hard axis.

No metamagnetic transition observed in Cu0.98Mn0.96As, indicating sensitivity to Cu vacancies.

Abstract

The orthorhombic antiferromagnetic compound CuMnAs was recently predicted to be an antiferromagnetic Dirac semimetal if both the Ry gliding and S2z rotational symmetries are preserved in its magnetic ordered state. In our previous work on Cu0.95MnAs and Cu0.98Mn0.96As, we showed that in their low temperature commensurate antiferromagnetic state the b axis is the magnetic easy axis, which breaks the S2z symmetry. As a result, while the existence of Dirac fermions is no longer protected, the polarized surface state makes this material potentially interesting for antiferromagnetic spintronics. In this paper, we report a detailed study of the anisotropic magnetic properties and magnetoresistance of Cu0.95MnAs and Cu0.98Mn0.96As. Our study shows that in Cu0.95MnAs the b axis is the easy axis and the c axis is the hard axis. Furthermore, it reveals that Cu0.95MnAs features a spin-flop phase transition at high temperatures and low fields when the field is applied along the easy b axis, resulting in canted antiferromagnetism. However, no metamagnetic transition is observed in Cu0.98Mn0.96As, indicating that the magnetic interactions in this system are very sensitive to Cu vacancies and Cu/Mn site mixing.