Magnetic diversity in stable and metastable structures of CrAs

We present results of electronic structure calculations of the bulk properties of CrAs. The crystalline structures of CrAs are investigated by the use of ab initio calculations with an unbiased swarm structural search under ambient and high pressure. Both the double helimagnetic and nonmagnetic phases in the neutron experiment are obtained and the pressure dependence of the magnetic phase transition is predicted. The $Pnma$ structure is the most stable structure below 33.1 GPa, meanwhile a magnetic phase transition of helimagnetic$\ensuremath{\rightarrow}$antiferromagnetic$\ensuremath{\rightarrow}$nonmagnetic is observed. The system tends to be antiferromagnetic after the double helimagnetic state near the optimal superconductivity regime without a crystal phase transition, which suggests that antiferromagnetic correlations between neighboring exchange interactions may be essential for the emergence of superconductivity in CrAs rather than a structural phase transition. Furthermore, the present results show that the $Pnma$ phase undergoes a pressure-induced phase transition to a cubic $P{2}_{1}3$ phase at 33.1 GPa. In addition, three low-enthalpy phases with a diverse magnetic order are identified as metastable states under ambient pressure. As the analytical results of the electronic structure, the three metastable structures, $P\overline{6}m2$ type A, $P\overline{6}m2$ type B, and $P4/nmm$, are antiferromagnetic, nonmagnetic, and ferromagnetic, respectively. An explanation for the interesting difference in the spin polarization is sought, in particular, for the covalent-ionic interactions between Cr and As atoms. The present results elucidate the structural and electronic properties of CrAs, and offer major implications as regards the diverse magnetic behaviors of CrAs.