Perpendicular Magnetic Anisotropy in FeRh Thin Films with Coexisting Magnetic Phases

This work reveals the evolution of perpendicular magnetic anisotropy in FeRh thin films during the antiferromagnetic‐ferromagnetic phase transition. Temperature‐dependent measurements and magnetic domain imaging demonstrate reorientation of magnetic moments from out‐of‐plane to in‐plane, driven by competition between magnetocrystalline anisotropy and shape anisotropy. These findings demonstrate the potential of FeRh in tunable spintronic applications. Abstract The advantages of high integration density, energy efficiency, and enhanced stability make the realization of perpendicular magnetic anisotropy (PMA) in single‐layer films a crucial step toward the development of advanced spintronic devices. A theoretical study predicted that the magnetic easy axis of FeRh film would reorient from out‐of‐plane (OP) to in‐plane (IP) directions during the antiferromagnetic‐ferromagnetic (AF‐FM) phase transition. However, few studies have observed an OP magnetic anisotropy in FeRh films. In this work, a continuous reorientation of the magnetic easy axis from OP to IP directions in FeRh film during its AF‐FM phase transition is demonstrated. Additionally, the anisotropy transition temperature increases with the film thickness. According to the magnetic domain imaging, the nucleation and initial growth of the FM domains at the AF state are dominated by magnetocrystalline anisotropy, leading to an OP easy axis in the FeRh thin film. With increasing temperature, shape anisotropy progressively dominates the magnetic properties of FeRh film, shifting the magnetic easy axis from OP to IP orientations. These findings not only demonstrate a novel anisotropy transition behavior in FeRh films, but also successfully induce PMA in such thick single‐layer films, providing critical experimental insights for the application of FeRh in spintronic devices. This work reveals the evolution of perpendicular magnetic anisotropy in FeRh thin films during the antiferromagnetic-ferromagnetic phase transition. Temperature-dependent measurements and magnetic domain imaging demonstrate reorientation of magnetic moments from out-of-plane to in-plane, driven by competition between magnetocrystalline anisotropy and shape anisotropy. These findings demonstrate the potential of FeRh in tunable spintronic applications. Abstract The advantages of high integration density, energy efficiency, and enhanced stability make the realization of perpendicular magnetic anisotropy (PMA) in single-layer films a crucial step toward the development of advanced spintronic devices. A theoretical study predicted that the magnetic easy axis of FeRh film would reorient from out-of-plane (OP) to in-plane (IP) directions during the antiferromagnetic-ferromagnetic (AF-FM) phase transition. However, few studies have observed an OP magnetic anisotropy in FeRh films. In this work, a continuous reorientation of the magnetic easy axis from OP to IP directions in FeRh film during its AF-FM phase transition is demonstrated. Additionally, the anisotropy transition temperature increases with the film thickness. According to the magnetic domain imaging, the nucleation and initial growth of the FM domains at the AF state are dominated by magnetocrystalline anisotropy, leading to an OP easy axis in the FeRh thin film. With increasing temperature, shape anisotropy progressively dominates the magnetic properties of FeRh film, shifting the magnetic easy axis from OP to IP orientations. These findings not only demonstrate a novel anisotropy transition behavior in FeRh films, but also successfully induce PMA in such thick single-layer films, providing critical experimental insights for the application of FeRh in spintronic devices. Advanced Science, Volume 12, Issue 42, November 13, 2025.