Influence of coercivity and relative orientation of magnetization on reversible permeability

Magnetic fields affect magnetization by combinations of vector rotation and displacement of domain walls. Rotation is opposed by the prevailing anisot ropy while wall displacement is resisted by factors associated with materia l heterogeneity. The extent of each process depends not only on the relativ e strengths of their respective opposing influences but also on the field o rientation relative to the moment distribution. Comparison of measured valu es of reversible susceptibility chi in samples magnetically processed to ob tain different distributions of domain orientations and densities of domain walls, inform on the extent of each process. Analysis predicts that materi als of moderate coercivity, dominated by cubic crystal anisotropy, should e xhibit maximum chi when remanently magnetized transversely to a probing fie ld and minimum chi when remanently magnetized parallel to the field. Experi mental measurements support this model. Results show strong correlations wi th remanence ratios. (C) 2000 American Institute of Physics. [S0021-8979(00 )41108-4].