Lorentz microscopy study on the magnetization reversal process in Co-Zr-O nanogranular magnetic films

The domain structure and the magnetization reversal process in Co₇₁Zr₁₃O₁₆ granular thin film, governed by a perpendicular anisotropy, are reported. Pattern of maze domains is observed, and the configuration is refined by the surface magnetic charges with function of specimen thickness. The wall energy is reduced by the low effective anisotropy and the exchange constant mediated by the amorphous layer. The magnetization reversal process is characterized by two magnetization rotation and one Barkhausen jump processes. The Barkhausen jumps easily take place at "Y" junctions of the stripe domains, where the distribution of the surface charges is irregular; the magnetization rotations are nonuniform in order to meet the requirement of the decrease in the demagnetization energy. 360° domain walls are found after Barkhausen jumps, indicating some pinning sites in the film.