Magnetic field-controlled lattice thermal conductivity in MnBi2Te4

TL;DR

This study demonstrates that magnetic fields can control the lattice thermal conductivity in MnBi2Te4 by inducing phase changes, revealing a new method to manipulate heat transport in magnetic materials.

Contribution

It introduces a novel approach to modulate thermal conductivity via magnetic field-induced phase transitions in MnBi2Te4, linking magnon-phonon interactions to thermal transport.

Findings

Thermal conductivity varies with magnetic field across different magnetic phases.

Magneto-Seebeck, Nernst, and thermal Hall effects are characterized.

Field-induced changes in magnon gap influence phonon scattering.

Abstract

Phonon properties and the lattice thermal conductivity are not generally understood to be sensitive to magnetic fields. Using an applied field to change MnBi2Te4 between antiferromagnetic (AFM), canted (CAFM) and ferromagnetic (FM) phases we discovered a new way to control the lattice thermal conductivity, generating both a positive and a negative magnetic field dependence. We report the field dependence of the thermal conductivity, k, in the in-plane direction under an applied magnetic field along the cross-plane direction in MnBi2Te4 from 2K to 30K. k decreases with field in the AFM phase, saturates in the CAFM phase, and increases with field in the FM phase. We explain this in terms of the field-induced changes of the magnon gap which modifies which magnon-phonon scattering processes are allowed by energy conservation. We also report magneto-Seebeck coefficient, Nernst coefficient and thermal Hall data measured in the same configuration. This finding may open a way to design magnetically controlled heat switches.