Orbital-Spin Structure and Coupling to Lattice in RTiO$_3$ with R=La,Pr,Nd and Sm

TL;DR

This paper investigates the origin of antiferromagnetism in RTiO$_3$ compounds, showing that GdFeO$_3$-type distortions lift orbital degeneracy and influence magnetic properties, with implications for understanding orbital-spin coupling.

Contribution

It reveals that GdFeO$_3$-type distortion universally controls orbital-spin structure in RTiO$_3$, competing with Jahn-Teller effects, and clarifies the stabilization of AFM(G) in LaTiO$_3$.

Findings

GdFeO$_3$-type distortion lifts $t_{2g}$ degeneracy at Ti 3d orbitals.

The orbital-spin structure aligns with experimental neutron scattering data.

GdFeO$_3$-type distortion universally influences magnetic and orbital properties.

Abstract

The origin of the G-type antiferromagnetism (AFM(G)) and puzzling properties of RTiO$_3$ with R=La are studied. We clarify that the crystal field from La caused by the GdFeO$_3$-type distortion lifts the $t_{2g}$ degeneracy at Ti 3d orbitals. The lift stabilizes the AFM(G) with spin-exchange constant in agreement with neutron scattering results. The orbital-spin structures for R=Pr, Nd and Sm are also consistent with experiments. We propose that the GdFeO$_3$-type distortion has a universal mechanism of controlling orbital-spin structure competing with the Jahn-Teller (JT) mechanism.