Suppressing Phonon-Magnon Scattering Increases Thermal Conductivity in Gadolinium near its Curie Temperature*

Thermal switches with a tunable thermal conductivity show great potential in contemporary thermal management. Manipulating thermal transport properties through magnetic fields has been accomplished in materials that exhibit high magnetoresistance. However, it is generally understood that the lattice thermal conductivity attributed to phonons is not significantly impacted by the presence of magnetic fields. In this study, we demonstrate the significant impact of spin-phonon scattering on the thermal conductivity of the rare-earth metal gadolinium. We experimentally observed an unsaturated linear increase in thermal conductivity with an external magnetic field up to 9 T around its Curie temperature (293 K). We isolated the contribution of electronic thermal conductivity, which did not account for the observed change. Using spin-lattice dynamics simulations, we showed that the reduced scattering of phonons by magnons at large magnetic fields led to the observed change in thermal conductivity. This result suggests that phonon-magnon scattering in ferromagnetic materials can be utilized to tune the thermal conductivity, opening the door to innovative magnetic-field-controlled thermal switches.