Atypical Magnetic, Electrical, and Magnetotransport Behaviors of Bismuth Films

• Main Authors: Hong-Xian Wang, 王鴻憲
• Other Authors: 郭博成
• Format: Others
• Language: zh-TW
• Published: 2004
• Online Access: http://ndltd.ncl.edu.tw/handle/98344996005954834462

碩士 === 國立臺灣大學 === 材料科學與工程學研究所 === 92 === In this thesis, we investigated the influence of crystalline orientation of Bi films, and the time dependant magnetic and magnetotransport behaviors of Fe-Bi films. First, the different crystalline orientations of Bi films can be obtained from growing on selected substrates such as Si(100), Si(110), and Si(111), which are prepared with dc magnetron sputtering followed by post-annealing. It was found that the ordinary magnetoresistance (OMR) effect to be oriented dependent. Furthermore, at very low temperature (0.3K), the Bi films exhibit Shubnikov-de Haas (SdH) oscillation; it was due to the Landau quantization of the cyclotron orbits of the carriers. Because the Fermi surface of Bi is highly anisotropic, the SdH oscillations exhibit different periods when the magnetic field is applied along different orientation. For Fe-Bi films, we found that the magnetic and magnetotransport properties of the samples will change with time. This is because that the Fe-Bi formed a metastable solid solution phase during the sputtering process, and different concentrations of Fe yield different rates of magnetic variation. Furthermore, the as-prepared films exhibit a large out-of-plane magnetic anisotropic property and the OMR effect. Due to aging precipitation, the magnetic anisotropy and the OMR decrease and eventually vanish as the duration increases. In addition, with the precipitation process, a magnetic dead layer will form on the surface of Fe nano-grains, it will severely reducing the magnetization and increasing the coercivity. On the contrary, Co-Bi films do not exhibit evidently time-dependent behavior.