Interplay of orbitally polarized and magnetically ordered phases in doped transition metal oxides

TL;DR

This paper explores how orbitally polarized and magnetic phases interact in doped transition metal oxides, analyzing their stability and the influence of Hund's coupling and crystal field effects.

Contribution

It provides a mean-field analysis of magnetic instabilities and orbital polarization in a two-dimensional e_g electron model, highlighting the roles of Hund's coupling and crystal field splitting.

Findings

Orbitally polarized states can coexist with ferromagnetic or antiferromagnetic order.

Hund's exchange coupling J_H influences the stability of magnetic phases.

Crystal field splitting E_z affects the orbital polarization and phase competition.

Abstract

We investigate the magnetic instabilities of the two-dimensional model of interacting e_g electrons for hole doping away from two electrons per site in the mean-field approximation. In particular, we address the occurrence of orbitally polarized states due to the inequivalent orbitals, and their interplay with ferromagnetic and antiferromagnetic spin order. The role played by the Hund's exchange coupling J_H and by the crystal field orbital splitting E_z in stabilizing one of the competing phases is discussed in detail.