Possible ferrimagnetism and ferroelectricity of half-substituted rare-earth titanate: A first-principles study on Y0.5La0.5TiO3

Titanates with the perovskite structure, including ferroelectrics (e.g., BaTiO₃) and ferromagnetic ones (e.g., YTiO₃), are important functional materials. Recent theoretical studies predicted multiferroic states in strained EuTiO₃ and titanate superlattices, the former of which has already been experimental confirmed. Here, a first-principles calculation is performed to investigate the structural, magnetic, and electronic properties of Y half-substituted LaTiO₃. Our results reveal that the magnetism of Y_0.5La_0.5TiO₃ sensitively depends on its structural details because of the inherent phase competition. The lowest energy state is the ferromagnetic state, resulting in 0.25 μB/Ti. Furthermore, some configurations of Y_0.5La_0.5TiO₃ exhibit hybrid improper polarizations, which can be significantly affected by magnetism, resulting in the multiferroic properties. Because of the quenching disorder of substitution, the real Y_0.5La_0.5TiO₃ material with random A-site ions may exhibit interesting relaxor behaviors.