Mechanically induced anisotropy and its effect on magnetic permeability in single crystal ferrites

Magnetic anisotropy and initial permeability in worked Mn-Zn and Mn-Fe ferrite single crystals are investigated in connection with the average magnetostriction constant λs. These data are compared with those obtained for etched specimens. Induced anisotropy is observed for all of the worked specimens and is proportional to λs, i.e., its origin should be the magnetoelastic energy λσ induced by stress σ remaining in the worked specimens. The ratio of initial permeability, μi(as-worked)/μi(etched), at room temperature, is found to increase with increasing λ111in a low frequency range and to be greater than unity when |λ111/λ100|> 3. The second peak in μi- T curves shifts with lapping to lower temperatures for the specimens with |λ111/λ100|<3, while to higher temperatures where |λ111/λ100|<3. Such phenomena are discussed in terms of domain wall energy affected by lapping-induced anisotropy.