Ferromagnetic polar metals via epitaxial strain: A case study of SrCoO3

While polar metals are a metallic analogue of ferroelectrics, magnetic polar metals can be considered as a metallic analogue of multiferroics.There have been a number of attempts to integrate magnetism into a polar metal by synthesizing new materials or heterostructures.Here we use a simple yet widely used approach-epitaxial strain in the search for intrinsic magnetic polar metals.Via first-principles calculations, we study strain engineering of a ferromagnetic metallic oxide SrCoO 3 , whose bulk form crystallizes in a cubic structure.We find that under an experimentally feasible biaxial strain on the ab plane, collective Co polar displacements are stabilized in SrCoO 3 .Specifically, a compressive strain stabilizes Co polar displacements along the c axis, while a tensile strain stabilizes Co polar displacements along the diagonal line in the ab plane.In both cases, we find an intrinsic ferromagnetic polar metallic state in SrCoO 3 .In addition, we also find that a sufficiently large biaxial strain (> 4%) can yield a ferromagnetic-to-antiferromagnetic transition in SrCoO 3 .Our work demonstrates that in addition to yielding emergent multiferroics, epitaxial strain is also a viable approach to inducing magnetic polar metallic states in quantum materials.