Strategy to Induce Multiferroic Property in (RTiO3 )n /(RVO3 )n Superlattices: A First-Principles Study.

Abstract

By first-principles calculations, lanthanide contraction is applied on a 1/1 (with symmetric center) and a 2/2 (with non-centrosymmetric polar structure) RTiO3 /RVO3 superlattices to realize quasi-continuous structural distortion modulation. The strong correlations of microscopic structural distortion, magnetic coupling and charge disproportionation accompanying metal-insulator transition (MIT) are clarified. It is found that the effect of lanthanide contraction on the 1/1 and 2/2 RTiO3 /RVO3 superlattices can induce ferromagnetic to antiferromagnetic transition within ab VO2 plane and the MIT occurs within these superlattices. And the MIT phenomenon is attributed to the charge disproportionation on V sites caused by the magnetic coupling transition. More structural distortion in the 2/2 RTiO3 /RVO3 superlattice is necessary than that of the 1/1 RTiO3 /RVO3 superlattice to induce the similar magnetic and MIT transition originating from the smaller interface/volume ratio. Based on these results, combining lanthanide contraction and epitaxial strain effects, multiferroic property is realized on 2/2 YTiO3 /YVO3 superlattice. Among all the structural parameters, aspect ratio c/a and Ti-O-V bond angles along the [001] direction are found to play the vital roles in the relevant transition process. Therefore, our calculations provide a microscopic guidance to design and synthesize new multiferroic materials.