不同结构多层膜中巨磁阻抗效应的研究

Research on Giant Magneto-Impedance Effect in Multilayered Films with Different Structure

研究了封闭式和开放式ＦｅＳｉＢ／Ｃｕ／ＦｅＳｉＢ多层膜以及Ｃｕ／ＦｅＳｉＢ／Ｃｕ多层膜中的巨磁阻抗效应。实验结果表明：多层膜的不同结构对巨磁阻抗效应影响很大。改变外加磁场，封闭式ＦｅＳｉＢ／Ｃｕ／ＦｅＳｉＢ多层膜中阻抗变化最大，开放式ＦｅＳｉＢ／Ｃｕ／ＦｅＳｉＢ多层膜次之，而Ｃｕ／ＦｅＳｉＢ／Ｃｕ多层膜中阻抗几乎不变。三组多层膜中不同的阻抗特征可用多层膜的具体结构解释：在封闭式多层膜内，磁路形成密封结构，使泄漏到多层膜外面空间的磁通大大减少；在 Ｃｕ／ＦｅＳｉＢ／Ｃｕ多层膜中，上下两铜层在铁磁薄膜内产生的总磁场近似为零，外加磁场的改变不能引起其阻抗发生变化。对于封闭式ＦｅＳｉＢ／Ｃｕ／ＦｅＳｉＢ多层膜，在１００ｋＨｚ到１ＭＨｚ时就能够出现较大的阻抗变化比值，最大阻抗变化比值出现在３ＭＨｚ。开放式ＦｅＳｉＢ／Ｃｕ／ＦｅＳｉＢ多层膜阻抗特性与封闭式类似，但比值只是封闭式多层膜的１／３。

Giant magneto-impedance (MI) of films with three types of multilayered structure has been investigated. Two of three are FeSiB/Cu/FeSiB films with closed and open structure, respectively, and the third type is Cu/FeSiB/Cu film with open structure. The experimental results show that, the FeSiB/Cu/FeSiB film with closed structure has the largest impedance change ratio of these three types, whereas the MI ratio in Cu/FeSiB/Cu film is the smallest. This difference can be contributed to their different structure designs. The film with closed structure posses a closed magnetic circuit, thus less magnetic flux leaks into the out space. When the total magnetic field is almost zero in Cu/FeSiB/Cu film, the impedance changes little. The impedance of the FeSiB/Cu/FeSiB film with closed structure changes remarkably in the frequency range from 100 kHz to 1 MHz, however, the MI effect in single FeSiB film with same thickness is very weak. The behavior of impedance spectra of FeSiB/Cu/FeSiB film with open structure is similar to the closed one, but the maximum MI ratio is only one-third of that in closed multilayered film.