(X=Cd, Zn): elucidating the interplay of crystallographic structure, magnetism, and topology*

A particular family of materials containing Eu are an interesting set of compounds for studying the interplay between structure, magnetism, and topology. To elucidate the factors that control their resistive anisotropy, we are studying EuCd₂As₂ compared to its analogue EuZn₂As₂. Replacing Cd with Zn reduces the spin-orbit coupling, the $d$-electrons are more localized, and the Nèel-temperature increases by a factor of two, but DFT calculations show strikingly small total energy differences (∼5 meV) between different magnetic configurations for both EuCd₂As₂ and EuZn₂As₂. The implication for experiments is that the magnetic ground-state of EuX₂As₂ can be manipulated easily by external pressure, strain, or disorder, making EuX₂As₂ an exciting platform for tuning a topological bandstructure through the magnetic order.