Research for Electric-field-driven Magnetooptical Devices based on Electromagnetic Effect

本文报道了Bi2O_3-Fe_2O_3-PbTiO_3三元系铁磁纳米复合氧化物溅射薄膜的电导率ε_r‘随外加磁场H的变化(磁电容效应)，并观察到小交流磁场ΔP_n(ω)引起的电极化。为了解释这些实验结果，我们提出了一个基于分散在介电基质中的铁磁纳米团簇的磁化旋转模型。然而，当使用硅片作为衬底时，在薄膜-硅界面上形成了归因于MIS结构的耗尽层，这严重影响了磁导率Δε_r‘(H)的磁场敏感部分的测量。为了完全消除这一现象，我们采用了重掺杂n^+-Si晶片(p=0.0016Ωcm)作为衬底，这意味着我们能够在很宽的频率范围内获得准确的Δε_r‘(H)值。此外，我们还测量了薄膜的Δε_r‘(H)与饱和磁化强度4πM_S的温度关系，以寻求这种电磁效应的机制，结果发现Δεr’(H)与4πM_s之间存在着密切的相关性。遗憾的是，由于在耐热玻璃衬底上沉积的多层膜(ITO/磁性薄膜/ITO)在热处理后导致电极之间的短路，因此没有检测到信号。因此，我们目前计划用硅衬底和ITO上电极来制备反射型样品。

We reported that the electric permeability ε_r' of ferromagnetic nanocomposite oxide sputtered films with a Bi2O_3-Fe_2O_3-PbTiO_3 ternary system is subject to change with an external magnetic field H (magnetocapacitance effect) and that electric polarization induced by a small ac magnetic field, ΔP_n(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 Δε_r'(H). In order to eliminate this completely, we used heavily doped n^+-Si wafers (p = 0.0016 Ωcm) as substrates, by which means we were able to obtain accurate Δε_r'(H)-value for a wide range of frequencies. In addition, we measured the temperature dependence of Δε_r'(H)and the saturation magnetization, 4πM_S, 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 4πM_S.We tried to measure Faraday spectra of the film applied electric field using the transmission type samples. Unfortunately, no signal was detected, since the multilayer film (ITO/magnetic film/ ITO) deposited on a heat-resistant glass substrate caused short circuit between electrodes after annealing. As a result, we presently plan to fabricate the reflection-type sample with a Si substrate and an ITO upper electrode.