Heat switch effect in an antiferromagnetic insulator Co$_3$V$_2$O$_8$

TL;DR

This study demonstrates a magnetic field-controlled heat switch effect in Co$_3$V$_2$O$_8$, where thermal conductivity can be dramatically increased or decreased by magnetic transitions, enabling potential thermal management applications.

Contribution

The paper reveals a large-scale heat switch effect in an antiferromagnetic insulator driven by magnetic field-induced suppression or enhancement of phonon thermal conductivity.

Findings

Magnetic field can increase thermal conductivity up to 100 times at 7.5 K.

Magnetic field can suppress thermal conductivity to about 8% at certain transitions.

Thermal conductivity is strongly affected by magnetic phase transitions and field orientation.

Abstract

We report a heat switch effect in single crystals of an antiferromagnet Co$_3$V$_2$O$_8$, that is, the thermal conductivity ($\kappa$) can be changed with magnetic field in an extremely large scale. Due to successive magnetic phase transitions at 12--6 K, the zero-field $\kappa(T)$ displays a deep minimum at 6.7 K and rather small magnitude at low temperatures. Both the temperature and field dependencies of $\kappa$ demonstrate that the phonons are strongly scattered at the regime of magnetic phase transitions. Magnetic field can suppress magnetic scattering effect and significantly recover the phonon thermal conductivity. In particular, a 14 T field along the $a$ axis increases the $\kappa$ at 7.5 K up to 100 times. For $H \parallel c$, the magnitude of $\kappa$ can be suppressed down to $\sim$ 8% at some field-induced transition and can be enhanced up to 20 times at 14 T. The present results demonstrate that it is possible to design a kind of heat switch in the family of magnetic materials.