An Eddy-Current Model Describing the Frequency Dependence of the Coercivity of Polycrystalline Galfenol

Fe₈₁Ga₁₉ is a high magnetostrictive material which exhibits soft magnetic behavior. The hysteresis loops of different heat treated Fe₈₁Ga₁₉ ring-shaped samples were measured as a function of the frequency. The frequency dependence of the coercivity H_c was analyzed using different eddy-current-based models. The obtained results need either an unrealistic high permeability in order to describe the experimental H_c(f) or a hypothetically oversized sample cross section. This shows that classical eddy currents are not sufficient to describe H_c(f) . The effect of anomalous eddy currents is more important for this material. A similar result is obtained analyzing the frequency dependence of the losses.