Contrasting magnetothermal conductivity in sibling Co-based honeycomb-lattice antiferromagnets

TL;DR

This study compares the magnetothermal conductivity of two similar Co-based honeycomb antiferromagnets, revealing significant differences in heat transport behavior linked to magnetic excitations and non-magnetic ion effects.

Contribution

It uncovers contrasting magneto-thermal conductivity behaviors in sibling compounds, highlighting the role of magnetic excitations and non-magnetic ions in heat transport.

Findings

Co4Ta2O9 shows 550% MTC enhancement at 9 T

Co4Nb2O9 exhibits only ~30% MTC change

Differences are due to distinct magnetic excitation evolution

Abstract

Honeycomb-lattice antiferromagnets have attracted wide attention for exploration of exotic heat transport and their interplay with magnetic excitations. In this work, we have revealed a contrasting behavior in the magneto-thermal conductivity (MTC) between two Co-based honeycomb-lattice magnets Co4M2O9 (M = Nb, Ta), despite their identical lattice structures and quite similar magnetism. Co4Ta2O9 exhibits enhanced MTC of about 550% at 9 T of an in-plane magnetic field, comparable to other honeycomb-magnets, while MTC for Co4Nb2O9 reaches only ~30%. This marked difference is ascribed to distinct features in the field-induced evolution of magnetic excitations that resonantly scatter phonons. This finding sheds light on implicit impacts of non-magnetic ions on thermal transport, and hints at the potential for broad heat-transport tunability while preserving magnetism and lattice structures.