The magnetic structure of the Jahn-Teller System LaTiO3

TL;DR

This paper models how Jahn-Teller distortions influence magnetic interactions in LaTiO3, revealing the orbital order's role in determining magnetic ground states through superexchange calculations.

Contribution

It introduces a localized superexchange model incorporating Jahn-Teller effects and spin-orbit coupling to explain magnetic order in LaTiO3.

Findings

Magnetic order aligns with experimental observations.

Orbital order is confirmed as static and influences magnetic interactions.

Anisotropic exchange terms are derived from spin-orbit coupling.

Abstract

We investigate the effect of the experimentally observed Jahn-Teller distortion of the oxygen octahedra in LaTiO3 on the magnetic exchange. We present a localized model for the effective hopping between nearest-neighbor Ti ions and the intra-site Coulomb interactions, based on a non-degenerate orbital ground state due to the static crystal field. The latter corresponds to an orbital order which recently has been confirmed experimentally. Using perturbation theory we calculate, in addition to the Heisenberg coupling, antisymmetric and symmetric anisotropy terms of the superexchange spin Hamiltonian which are caused by the spin-orbit interaction. Employing our superexchange Hamiltonian, we deduce the magnetic order at low temperatures which is found to be in good agreement with experiment.