Structure, Magnetotransport, and Theoretical Study on the Layered Antiferromagnet Topological Phase EuCd2As2 under High Pressure

Rich nontrivial topological phases rooted in the interplay between magnetism and topology in the layered antiferromagnet EuCd2As2 have captured vast attention, especially the ideal Weyl semimetal state realized in the spin-polarized ferromagnetic (FM) structure driven by a moderate external magnetic field. In this work, combining magnetization, magneto-transport, and structure measurements under high pressure and first principles calculations, this study finds that the pressure can drive the in-plane antiferromagnetic structure of EuCd2As2 across an intermediate in-plane FM structure then into the out-of-plane FM structure. This study also finds butterfly-shaped MR and anomalous Hall effect under large pressure, which may support the pressure-driven FM state. High-pressure angle-dispersive X-ray diffraction and X-ray absorption near-edge spectroscopy measurements exclude structure transition and/or change of Eu2+ valence state as sources for the magnetic phase transitions. Alternatively, apparently reduced axial ratio (c/a) and compressed Eu-layer space distance should play important roles. Interestingly, the calculations unveil that the out-of-plane FM structure hosts only one pair of Weyl nodes around the Fermi level, suggesting that pressure can be an alternative way to realize the ideal Weyl semimetal state in EuCd2As2 and will be useful for exploring exotic topological properties in such layered magnetic topological phase with strongly competing magnetic exchanges.