鉄基強磁性酸化物スパッタ薄膜における磁界誘導電気分極

Abstract

In our previous papers, it was reported that the dielectric permeability er' is subject to change with magnetic field H, Δer'(H) in ferromagnetic nano-composite oxide films with the Bi2O3-Fe2O3-PbTiO3 ternary system. In the present study, we first measured the temperature dependence of er' and Δer'(H). Both quantities increase rapidly above 50°C, which suggests that softening of the glass network of the dielectric matrix takes place at this temperature to promote the charge displacement giving rise to the dielectric polarization. Next, we measured the magnetic field dependence of the displacement current Jd(H) to confirm whether the permeability change with magnetic field Δer'(H) is intrinsic. It was found that Jd(H) is also subject to change in a similar manner to Δer'(H), indicating that the charge displacement assisted by H really occurs. Finally, we observed the dielectric polarization induced by applying a small ac magnetic field at room temperature. This is considered to be a new type of electromagnetic effect. To explain the experimental results, we propose a simple model based on magnetization rotation of ferromagnetic nano-clusters dispersed in a dielectric glassy matrix.