Electronic structure of double perovskite SrTi0.5Co0.5O3: order, disorder, and vacancy effects

Abstract

In this study, we investigate the electronic structure of the ordered/disordered double perovskite SrTi0.5Co0.5O3 (STCO) using density functional theory (DFT) and the full-potential linearized augmented plane wave method. Detailed structural and magnetic stability analysis revealed that Sr2TiCoO6 crystallizes in the tetragonal I4/m space group, in which Co4+ and Ti4+ ions are distributed in an alternating arrangement along three directions. Notably, Sr2TiCoO6 exhibits a half-metallic property and exhibits ferromagnetic (FM) behavior, originating from the Co4+-O2--Ti4+ bonds and the high spin state of cobalt. Additionally, a chemical/magnetic stability analysis was carried out to identify the ground state structure in disordered STCO. The investigation identified a two-dimensional-like configuration (referred to as STC5FM) characterized by ferromagnetic order. This particular arrangement represents the most chemically stable layered configuration, featuring a maximal occurrence of Co–O–Co chains. Thus, Co4+ ions exhibit an intermediate spin state following Goodenough-Kanamori-Anderson rules of ferromagnetic mechanism. Interestingly, this structure also displays ferromagnetism at room temperature, accompanying with semiconductor properties. The study also explored the impact of oxygen vacancies. Remarkably, the ferromagnetic attributes remain robust even in the presence of oxygen vacancies. Moreover, a transition from semiconductor to metal behavior becomes evident under these conditions.