CPOS Seminar: "Field-Controlled Thermal Switching at Room Temperature in Ferromagnets, Ferroelectrics, and Polymers"
Speaker: Fanghao Zhang, Postdoctoral Researcher, Liao Group, T.E.A. Lab @ UCSB, Department of Mechanical Engineering, UCSB
Controlling heat flow with external fields provides new opportunities for active and tunable thermal management. Previous demonstrations in thin films and solid solutions have shown reversible switching, but their small thermal resistance and extrinsic scattering limit both practical applications and mechanistic understanding. In this presentation, I will highlight our recent progress on developing field-driven thermal switches across distinct classes of materials. In ferromagnetic gadolinium near its Curie temperature, we demonstrate that applying magnetic fields up to 9 T leads to a pronounced and unsaturated increase in thermal conductivity. Spin-lattice dynamics simulations confirm that this effect arises from the suppression of phonon–magnon scattering, establishing a direct pathway for magnetic-field control of lattice heat transport. Turning to ferroelectrics, we investigate bulk single crystals to isolate intrinsic mechanisms. Our results reveal that electric-field-driven domain reconfiguration, rather than domain walls, governs thermal conductivity modulation. By engineering defect-mediated polarization switching, we achieve large and reversible thermal switching ratios at room temperature. Finally, I will present preliminary findings on the relaxor ferroelectric polymer P(VDF-TrFE-CFE), indicating its potential as a platform for field-controlled thermal switching. Together, these studies identify magnetic, ferroelectric, and polymer systems as complementary routes toward multifunctional thermal switches, enabling new approaches for thermal control in advanced technologies.
