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

本文报道了Bi_2O_3-Fe_2O_3-PbTiO_3三元系铁磁纳米复合氧化物溅射薄膜的磁导率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）引起的电极化现象。为了解释这些实验结果，我们提出了一个基于分散在电介质基质中的铁磁纳米团簇的磁化旋转的模型。然而，当用硅作衬底时，由于MIS结构在膜-硅界面上形成了一个耗尽层，严重影响了磁导率Δε r '（H）的磁场敏感部分的测量。为了完全消除这种现象，我们使用重掺杂的n^+-Si晶片（p = 0.0016 Ωcm）作为衬底，通过这种方法，我们能够在很宽的频率范围内获得精确的Δε_r '（H）值。此外，我们还测量了薄膜的Δε r '（H）和饱和磁化强度4πM_S随温度的变化关系，以探讨这种电磁效应的机理，结果发现Δε r'（H）和4πM_S之间存在密切的相关性。不幸的是，没有检测到信号，因为沉积在耐热玻璃基板上的多层膜（ITO/磁性膜/ ITO）在退火后引起电极之间的短路。因此，我们目前计划制造具有Si衬底和ITO上电极的反射型样品。

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.