Modeling of complex oxide materials from the first principles: systematic applications to vanadates RVO3 with distorted perovskite structure

TL;DR

This paper develops a first-principles effective modeling approach for complex oxides, specifically applied to vanadates RVO3, to analyze their electronic, magnetic, and orbital properties under various distortions.

Contribution

It introduces a systematic first-principles modeling method for vanadates RVO3, highlighting the analysis of spin, orbital states, and stabilization mechanisms of magnetic phases.

Findings

Orbital degeneracy lifting stabilizes C-type AFM state.

Crystal distortion influences magnetic state transitions.

Microscopic mechanisms involve crystal field and electron correlations.

Abstract

"Realistic modeling" is a new direction of electronic structure calculations, where the main emphasis is made on the construction of some effective low-energy model entirely within a first-principle framework. Ideally, it is a model in form, but with all the parameters derived rigorously, on the basis of first-principles electronic structure calculations. The method is especially suit for transition-metal oxides and other strongly correlated systems, whose electronic and magnetic properties are predetermined by the behavior of some limited number of states located near the Fermi level. After reviewing general ideas of realistic modeling, we will illustrate abilities of this approach on the wide series of vanadates RVO3 (R= La, Ce, Pr, Nd, Sm, Gd, Tb, Yb, and Y) with distorted perovskite structure. Particular attention will be paid to computational tools, which can be used for microscopic analysis of different spin and orbital states in the partially filled t2g-band. We will explicitly show how the lifting of the orbital degeneracy by the monoclinic distortion stabilizes C-type antiferromagnetic (AFM) state, which can be further transformed to the G-type AFM state by changing the crystal distortion from monoclinic to orthorhombic one. Two microscopic mechanisms of such a stabilization, associated with the one-electron crystal field and electron correlation interactions, are discussed. The flexibility of the orbital degrees of freedom is analyzed in terms of the magnetic-state dependence of interatomic magnetic interactions.