Oscillating Gadolinium Thermal Diode Using Temperature‐Dependent Magnetic Forces

Abstract High‐performance thermal diodes would enable improved waste heat scavenging and thermal management systems. Prior study has indicated that the temperature ( T )‐dependent magnetic response of ferromagnets near the Curie temperature provides a potential mechanism for thermal rectification via thermally induced mechanical oscillations between hot and cold surfaces, but the rectification was not investigated in a macroscopic device. Here, a centimeter‐scale oscillating gadolinium thermal diode (OGTD) is constructed with steady‐state thermal rectification ratios (γ) as large as γ = 23 in air and γ = 16 in vacuum. In the forward mode when the top surface is warmer than 26 °C and the bottom surface is colder than 20 °C, an unstable balance between gravitational forces and T ‐dependent magnetic forces causes a shuttle containing gadolinium to oscillate and transfer thermal energy. In the reverse mode, the shuttle does not oscillate and energy is transferred via parasitic conduction. The diode is durable over >10 3 oscillation cycles and can be used in thermal circuits for rapid thermal regulation in time‐varying environments or half‐wave thermal rectification with up to 50% of the ideal‐diode performance. The experiments show that the OGTD can achieve large γ in a convenient geometry and T range for thermal control applications.