Highly anisotropic magnon dispersion in Ca2RuO4: evidence for strong spin orbit coupling

TL;DR

This study reveals highly anisotropic magnon dispersion in Ca2RuO4, highlighting the significant role of spin-orbit coupling and orbital ordering in shaping magnetic excitations, with implications for understanding complex magnetic materials.

Contribution

The paper provides the first detailed inelastic neutron scattering analysis of Ca2RuO4's magnon dispersion, emphasizing the impact of strong spin-orbit coupling and orbital ordering.

Findings

Magnon dispersion well described by a Heisenberg model with J=8 meV

Large anisotropy gap caused by spin-orbit coupling

Orbital ordering and spin-orbit coupling are key factors

Abstract

The magnon disp ersion in Ca2RuO4 has been determined by inelastic neutron scattering on single crytals containing 1% of Ti. The dispersion is well described by a conventional Heisenberg model suggesting a local moment model with nearest neighbor interaction of J=8 meV. Nearest and next-nearest neighbor interaction as well as inter-layer coupling parameters are required to properly describe the entire dispersion. Spin-orbit coupling induces a very large anisotropy gap in the magnetic excitations in apparent contrast with a simple planar magnetic model. Orbital ordering breaking tetragonal symmetry, and strong spin-orbit coupling can thus be identified as important factors in this system.