Transverse susceptibility of nickel thin films with uniaxial anisotropy

A finite temperature Stoner-Wohlfarth model has been used to calculate the transverse susceptibility of an ensemble of ferromagnetic particles with distributed anisotropy. The simulated transverse susceptibility is in excellent agreement with data acquired from thin film samples of elemental nickel, deposited on 128° Y-cut LiNb0₃. A strong, well-defined, uniaxial anisotropy is induced in the nickel film by low temperature annealing. Three peaks in the transverse susceptibility are observed in both the measured and simulated data when the applied field is misaligned with the hard axis by a few degrees. Two broad, reversible peaks occur when the applied field is equal to the anisotropy field. A single, sharp irreversible peak occurs when the absolute value of the applied field is less than the anisotropy field, and is associated with a metastable magnetic state. The irreversible peak disappears when the applied field is well aligned with the hard axis. The observed transverse susceptibility is consistent with the theoretical predictions of Aharoni et al. and is therefore consistent with the Stoner-Wohlfarth model.