Thermal rectification via sequential deactivation of magnons

Abstract

Theoretically, a thermal rectifier is a solid state device which presents a greater heat flux in the forward than in the reverse thermal bias, Q+ > Q−. Ferromagnetic materials, which can exist in two magnetic states with distinct thermal conductivities, provide a unique opportunity to realize nonlinear thermal transport. Herein, by realizing a proof-of concept device consisting of manganites type La1-xSrxMnO3, we introduce a two-segment thermal diode that manipulates the heat via a sequential deactivation of magnons in each segment through their respective Curie temperatures Tc. Thermal measurements of the diode show that as the sequential magnetic transitions occur, the rectification factor increases. We interpret such an enhancement in the rectification factor due to drastic changes in the thermal conductance of the device as a consequence of the spin-disorder dominance above Tc. Furthermore, the results are validated via an analytical model within the framework of the Fourier law by using power law approximations of the temperature-dependent thermal conductivity of segments. Hence, sequential deactivation of magnons provides an alternative route so as to develop enhanced performance thermal rectifiers.