Orbitally driven spin reorientation in Mn-doped YBaCuFeO5

The oxygen-deficient layered perovskite YBaCuFeO5 (YBCFO) is a rare type-II multiferroic material where ferroelectricity, driven by incommensurate spiral magnetic order, believed to be achievable up temperatures higher than room temperature. A cycloidal order rather helical an essential ingredient for the existence of ferroelectricity in this material. Motivated recent experimental study on Mn-doped YBCFO plane was observed cant more towards crystallographic c-axis upon Mn doping at Fe sites parent compound, we performed detailed theoretical investigation using density functional theory calculations understand mechanism behind such spin reorientation. Our total energy calculations, within generalized gradient approximation plus U spin–orbit coupling approach, reveal that Fe/Cu moments indeed align compound. largest exchange interaction (Cu-Cu a−b plane) decrease systematically with concentration, reflecting lowering transition temperature seen experiments. Further, inter-bilayer Cu-Mn becomes ferromagnetic YBCFO, whereas corresponding Cu-Fe antiferromagnetic giving rise frustration commensurate order. Most importantly, our electronic structure because hybridization dz2 orbital, highest occupied Cu orbital as opposed dx2−y2 Therefore, believe occupancy out-of-plane-oriented place planar along frustrating drives spins YBCFO.