Heat switch effect in an antiferromagnetic insulator Co_3V_2O_8

摘要

We report a heat switch effect in single crystals of an antiferromagnet Co_3V_2O_8, that is, the thermal conductivity (κ) can be changed with magnetic field in an extremely large scale. Due to successive magnetic phase transitions at 12-6K, the zero-field κ(T) displays a deep minimum at 6.7 K and rather small magnitude at low temperatures. Both the temperature and field dependencies of κ 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 κ at 7.5 K up to 100 times. For H || c, the magnitude of κ can be suppressed down to ～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.