Temperature‐Induced Nonvolatile Switching through Thermal Hysteresis in a Gd ₃ Fe ₅ O ₁₂ /Ho ₃ Fe ₅ O ₁₂ Exchange‐Coupled Rare‐Earth Iron Garnet Bilayer

ABSTRACT Spintronic devices based on ferrimagnetic insulators (FMIs) offer promising approaches toward energy‐efficient magnetic memories. A critical challenge in this field is achieving reliable nonvolatile magnetic switching with minimal energy consumption. Temperature‐induced switching, which utilizes temperature modulation instead of electrical currents or magnetic fields, provides a compelling strategy. However, maintaining stable states without continuous energy input has remained problematic. Here, we demonstrate purely temperature‐induced nonvolatile magnetic switching using a bilayer composed of gadolinium iron garnet and holmium iron garnet. Using the longitudinal spin‐Seebeck effect, we probe the Fe sublattice magnetization states and identify significant thermal hysteresis driven by three key factors: (i) a crossover of magnetization from the distinct temperature dependences of the two layers, (ii) strong antiferromagnetic coupling at their interface, and (iii) intrinsic magnetic anisotropies. This hysteresis facilitates stable bistable magnetic states within a finite temperature range. By applying a moderate external magnetic field of 30 Oe, we achieve clear and stable switching with ±25 K temperature modulation. Furthermore, detailed energy analysis reveals that temperature‐induced switching requires up to 66‐fold less energy compared to conventional spin‐orbit torque switching in 100‐nm‐thick FMIs. Our findings indicate that temperature‐induced switching presents a viable, energy‐efficient alternative for magnetic memory applications.