Magnetic relaxation in Barium ferrite films with perpendicular anisotropy

Magnetic relaxation analysis have been carried out on barium ferrite films with perpendicular anisotropy, grown by pulsed laser deposition. Logarithmic behaviour on the time dependence of the magnetisation has been observed. The measured and corrected viscosity exhibit a large difference because of the contribution of the demagnetisation effect. At high fields, this difference is very much reduced because of the saturation which limits the susceptibility to very low values. Compared to the grain volume, the activation volume is small (Vac/Vgrain=0.1–0.2). This result can be explained by the incoherent rotation mode of the magnetisation reversal