Atomic resolution structure–property relation in highly anisotropic granular FePt-C films with near-Stoner-Wohlfarth behaviour

Chemically ordered and highly textured L10 FePt-C granular films are potential media for future heat-assisted magnetic recording. Vibrating sample magnetometry of such films in fields up to 14 T reveals a perpendicular coercivity of up to μ0HC=4.92 T and an anisotropy field of μ0HA=9.2 T, which translates to a (uni-axial) anisotropy constant as high as KU=5.3 MJ/m3. An analysis of the remanent magnetization and demagnetization curves shows that the spatially separated FePt nanoparticles act as a Stoner-Wohlfarth ensemble of uni-axial nanomagnets with negligible dipolar inter-particle coupling. The magnetic texture spread of 23° as determined from an analysis of the hard axis magnetization curve is found to be clearly larger than the structural texture width of roughly 3°. Aberration corrected high-resolution transmission electron microscopy reveals that the latter is due to the remaining roughness of the seed layer that causes the particle growth to nucleate at step edges of this layer.