Large Room‐Temperature Exchange Bias in Y ₃ Fe ₅ O ₁₂ via Antiparallel Exchange Interaction with Magnetically Pinned CoFe ₂ O ₄ Nanoparticles

The rapid expansion of data-driven technologies has intensified demand for energy-efficient and secure information processing platforms. Insulator-based spintronic devices, which leverage quantized spin waves (magnons), offer a promising solution. Among insulating materials, yttrium iron garnet (YIG; Y₃Fe₅O₁₂) is notable for its ultra-low magnetic damping; however, its exchange bias (EB) effect at room temperature remains inadequate for robust device operation. In this study, a new materials platform is developed by pairing YIG with cobalt ferrite (CFO; CoFe₂O₄), achieving a record-high exchange bias field (H_EB) of 59 ± 4 Oe at room temperature, as determined by angular-dependent ferromagnetic resonance measurements of YIG-CFO bulk composites. This large H_EB can be attributed to a strong antiparallel exchange interaction at the YIG-CFO interface. These findings indicate a promising route toward achieving strong EB effects in thin-film YIG-CFO systems and provide a straightforward materials strategy for engineering enhanced magnetic coupling in insulating systems.