Doping and pressure-driven structural transition in BiMnO3+δ from first principles

Abstract We investigate the changes in the electronic structure and magnetic properties of BiMnO 3 + δ accompanied the phase transition C 2 ∕ c → P 2 1 ∕ c which occurs either with an increase in the oxygen content or with external pressure applied. We have established that although both factors lead to similar structural changes, their mechanisms have reverse causal relationships. The application of pressure leads to the change in the volume of MnO 6 octahedra. The latter, due to strong p - d hybridization, leads to a decrease in the localization degree of manganese electrons, which causes the reduction in Mn magnetic moments. Meanwhile, when there is excess oxygen in the system, the reverse process occurs wherein the charge density redistribution leads to a decrease in the occupation number of the Mn- e g states causing the drop in the value of the local magnetic moments and, as a consequence, to the contraction in the lengths of the Mn-O bonds.