Interplay of uniform and random anisotropy in nanocrystalline soft magnetic alloys

The magnetization process in nanocrystalline Fe73Cu1Nb3Si16B7 ribbons with different magnitudes of a magnetic field induced transverse anisotropy was investigated by Kerr-microscopy and magnetic hysteresis measurements at room temperature and elevated temperatures. Comparing samples with strong (Ku ≈ 30 J/m3) and weak (Ku ≈ 3 J/m3) induced anisotropy Ku, we find significant differences in the magnetic microstructure, reflecting the interplay of the uniform, field induced and the random magneto-crystalline anisotropy. In particular for weak Ku, we find irregular magnetization patches within the wide regular domains connected to the induced anisotropy. These magnetization patches are fluctuating on the scale of a few micrometers and are interpreted in terms of the random anisotropy.