Theoretical evidence and chemical origin of the magnetism-dependent electrostructural coupling in La₂NiMnO₆

Abstract

Using first-principles density-functional calculations, we determine and analyze the Born effective charges Z^∗ that describe the coupling between electric field and atomic displacements for ferromagnetic double-perovskite compound, La₂NiMnO₆. We find that the Born effective charge matrix of Ni in La₂NiMnO₆, has an anomalously large antisymmetric component, whose magnitude reduces substantially upon change in the magnetic ordering between Ni and Mn, showing it to be a magnetism-dependent electrostructural coupling. We use a local picture of the electronic structure obtained with Wannier functions, along with its band-by-band decomposition to determine its electronic origin.