We previously reported that the electric permeability εr' of ferromagnetic nanocomposite oxide sputtered films with a Bi2O3-Fe2O3-PbTiO3 ternary system is subject to change with an external magnetic field H and that electric polarization induced by a small ac magnetic field, ΔPh(ω), is observed. To explain these experimental results, we proposed a model based on magnetization rotation of ferromagnetic nanoclusters dispersed in a dielectric matrix. However, it was found that, when Si-wafers are used as substrates, a depletion layer attributed to the MIS structure is formed in the film-to-Si interface, which seriously affects measurements of the magnetic-field-sensitive portion of the permeability Δεr'(H). In order to eliminate this completely, we used heavily doped n+-Si wafers (ρ = 0.0016 Ωcm) as substrates, by which means we were able to obtain accurate Δεr'(H)-value for a wide range of frequencies. In addition, we measured the temperature dependence of Δεr'(H) and the saturation magnetization, 4πMs, of a film to seek for the mechanism of this electromagnetic effect, as a result of which a close correlation was found to exist between Δεr'(H) and 4πMs.
