強磁性酸化物薄膜における磁界誘導電気分極の直流バイアス電圧依存性

Abstract

In the past several years, we have reported that electric susceptibility χ' is subject to change with external magnetic field H in ferromagnetic nano-composite oxide sputtered films with a Bi2O3-Fe2O3-PbTiO3 ternary system. The charge displacement current assisted by H and the electric polarization induced by applying a small ac magnetic field, ΔPh(ω), were measured to confirm whether the susceptibility change with magnetic field, Δχ'(H), is intrinsic.In the present study, we found that the detected ΔPh(ω) signal changes depending on both the direction of the magnetic field and the dc bias voltage applied perpendicular to the film plane. To explain these experimental results, we made some alterations to the previous model based on magnetization rotation. From capacitance vs. voltage measurement, it was found that, since we used Si-wafers as substrates, a depletion layer attributed to the MIS structure is formed in the film-to-Si interface. This effect could ultimately be eliminated by applying a forward-biased electric field.