Magnetocaloric-Effect-Enhanced Near-Field Magneto-optical Thermal Switch

The magnetocaloric effect is the change in temperature of a magnetic material in response to a change in its magnetization, mediated by an external magnetic field. Since the early 20th century, its main application has been magnetic refrigeration, which has the potential to outperform conventional liquid-vapor refrigerators. In this paper, we combine the magnetocaloric effect with magneto-optical control of near-field radiative heat transfer to introduce an alternative thermal switch with two tuning knobs: a magnetocaloric one that can adjust the temperature gradient and a magneto-optical one that can adjust the conductance of the gap between two materials participating in radiative heat transfer. We consider two representative material systems at room temperature: a Gd-SiC system with magnetocaloric tunability and a Gd-InAs system with both magnetocaloric and magneto-optical tunability. Our model predicts several different operating modes of the thermal switch enabled by the magnetocaloric effect, including one where the flow of heat is reversed. Simultaneously, the magneto-optical response of InAs enables fine-tuning of the spectral heat flux via control of the electromagnetic surface modes. Our work recontextualizes near-field radiative heat transfer between magnetic materials and serves as an example of combining an i-caloric effect (the thermal response of a material due to a change in an applied field i, where i = magneto-, elasto-, electro-, etc.) with a complementary mode of heat transfer to enable new thermal technologies.