On the pseudo-doublet ground state of the non-Kramers compound SrTm2O4 and its frustrated antiferromagnetic interactions

TL;DR

This study investigates the pseudo-doublet ground state of SrTm2O4, revealing distinct magnetic sublattices, frustrated antiferromagnetic interactions, and the system's persistent paramagnetism at low temperatures despite its complex ground state.

Contribution

It provides experimental evidence and theoretical modeling of the magnetic properties and interactions in SrTm2O4, highlighting the role of frustration and anisotropy in its magnetic behavior.

Findings

Distinct single-ion anisotropies for Tm3+ sites

Presence of frustrated antiferromagnetic interactions

System remains paramagnetic at low temperatures

Abstract

Here we present experimental evidence of the pseudo-doublet ground state of the non-Kramers compound SrTm2O4, based on specific heat, magnetic entropy and electron paramagnetic resonance. We demonstrate that the two crystallographic Tm3+ sites give rise to distinct single-ion anisotropies, and by extension, SrTm2O4 hosts two magnetic sublattices. Inelastic neutron scattering reveals low-lying dispersing crystal-field excitations, which we modelled using an effective charge model and mean field random phase approximation. The extracted magnetic exchange interactions are both antiferromagnetic and frustrated for both chains. Interchain magnetic exchange interactions are negligible. The strength of the magnetic exchange interactions in relation to the size of crystal field gaps, together with the frustration and low dimensionality, force the system to remain paramagnetic down to the lowest experimentally reachable temperature despite the pseudo-doublet nature of its ground state.