Spin-orbit coupling and magnetism in $\rm Sr_2CrO_4$

TL;DR

This paper investigates how spin-orbit coupling influences magnetic and orbital order in Sr2CrO4, revealing a transition from staggered to entangled orbital states and linking excitation energies to pressure-induced phase changes.

Contribution

It introduces a comprehensive analysis of spin-orbit effects on collective excitations in Sr2CrO4, highlighting a critical transition in orbital order driven by SOC.

Findings

Transition from staggered to entangled orbital order at critical SOC.

Energy scales of excitations correlate with pressure-induced transition temperatures.

Behavior of collective excitations matches high-pressure susceptibility and resistivity data.

Abstract

With octahedrally coordinated $t_{\rm 2g}$ orbitals which are active at filling $n=2$, the $\rm Sr_2CrO_4$ compound exhibits rich interplay of spin-orbital physics with tetragonal distortion induced crystal field tuning by external agent such as pressure. Considering both reversed and restored crystal field regimes, collective spin-orbital excitations are investigated in the antiferromagnetic state using the generalized self consistent + fluctuations approach including spin-orbit coupling (SOC). A transition is found from staggered to entangled orbital order at critical SOC value in the realistic regime. Behavior of the calculated energy scales of collective excitations with crystal field is in striking similarity to that of the transition temperatures with pressure as obtained from susceptibility and resistivity anomalies in high-pressure studies.