Size-dependent magnetic domain evolution in patterned FeRh films

Equiatomic B2-ordered FeRh alloy possesses unique metamagnetic phase transition above room temperature, which provides a promising route for emerging magnetic recording and spintronic applications when downsized into nanoscale. This paper presents a systematic investigation of magnetic domain in single crystal FeRh films patterned into nanoscale stripe, ring, and circle geometries to explore the evolution of involved transition behavior and magnetic anisotropy. When the characteristic size of the patterns approaches 100 nm, a pronounced supercooling phenomenon occurs; particularly in the circle patterns, the supercooling degree exceeds 15 K. This finding reveals a suppression of the conventional heterogeneity-driven antiferromagnetic nucleation mechanism by dimensional confinement related to the pattern area. Concurrently, the dimensional confinement reduces the demagnetization energy, which enables ferromagnetic FeRh to maintain robust perpendicular magnetic anisotropy up to 390 K and across a wide temperature window of 45 K. Our work not only provides a deep insight into the metamagnetic phase transition mechanism at nanoscale but also is beneficial for realizing novel device functionalities utilizing nanosized FeRh.