Designed Ferromagnetic, Ferroelectric Bi₂NiMnO₆

Abstract

A newly designed ferromagnetic, ferroelectric compound, Bi2NiMnO6, was prepared by high-pressure synthesis at 6 GPa. The crystal structure, as determined by synchrotron X-ray powder diffraction, is a heavily distorted double perovskite with Ni2+ and Mn4+ ions ordered in a rock-salt configuration. The presence of 6s2 lone pairs of Bi3+ ions and the covalent Bi−O bonds give ferroelectric properties with TCE of 485 K, while −Ni2+−O−Mn4+−O−Ni2+− magnetic paths lead to a ferromagnetism with TCM of 140 K. This simple material design to distribute two magnetic elements with and without eg electrons on B sites of Bi- and Pb-based perovkites can be applied to other Bi2M2+M‘4+O6 and Pb2M3+M‘5+O6 systems to search for newer ferromagnetic ferroelectrics.