Cation Order–Disorder Transition in Fe-Doped 6H-BaTiO3 for Dilute Room-Temperature Ferromagnetism

Abstract

Understanding the fundamental spin coupling mechanisms in dilute magnetic oxides is not possible without exact atomistic understanding of the solids. This is even more important for few systems that show dilute ferromagnetism at room temperature and could potentially be used in spintronic and multiferroic technologies. Here, we show the first known example of a cation ordering in hexagonal 6H-perovskites. Fe3+ ions in Fe-doped 6H-BaTiO3 are initially randomly distributed over two Ti4+ crystallographic sites but can be, by a prolonged heat treatment, ordered onto one of the sites. The cation ordering is driven by reduction in the electrostatic repulsion, which occurs when Fe3+ substitutes the highly charged Ti4+ ions that are located at unusual proximity to each other. We show that such a continuous order–disorder transition is associated with induction of the room-temperature dilute ferromagnetism.