Magnetoelastic coupling in RETiO3 (RE = La, Nd, Sm, Gd, Y)

TL;DR

This study investigates the intrinsic magnetoelastic coupling in RETiO3 compounds, revealing that orbital-lattice interactions are significant and vary with temperature and magnetic order, beyond structural distortions.

Contribution

It provides a detailed analysis showing that orbital-lattice coupling in RETiO3 is intrinsic and not solely due to structural distortions, with temperature-dependent effects linked to magnetic transitions.

Findings

Strong anomalies in thermal expansion near magnetic ordering.

Octahedral distortions depend on RE ionic radius.

Effects are most pronounced near magnetic crossover.

Abstract

A detailed analysis of the crystal structure in RETiO3 with RE = La, Nd, Sm, Gd, and Y reveals an intrinsic coupling between orbital degrees of freedom and the lattice which cannot be fully attributed to the structural deformation arising from bond-length mismatch. The TiO6 octahedra in this series are all irregular with the shape of the distortion depending on the RE ionic radius. These octahedron distortions vary more strongly with temperature than the tilt and rotation angles. Around the Ti magnetic ordering all compounds exhibit strong anomalies in the thermal-expansion coefficients, these anomalies exhibit opposite signs for the antiferromagnetic and ferromagnetic compounds. Furthermore the strongest effects are observed in the materials close to the magnetic cross-over from antiferromagnetic to ferromagnetic order.