| Summary: | 碩士 === 國立交通大學 === 電子物理系 === 91 === In the recent year , the ferromagnetic multilayer systems are being investigated popularly and intensively. It was utilized for magnetic read-head by IBM in 1991. People have realized that the intrinsic property, spin, of electron can play an important role in many aspects. Many spin-dependent mechanisms are valuable topics in the basic researches and have profound potentials in industrial application. The interfacial scatterings between ferromagnetic material and others are quite complicated but important attracting many scientists’attentions. In the dissertation, we discuss the influence of the covering layer on the electrical transport and the influence of oxidation on anisotropic magneto-transport in 2D magnetic film.
10nm thick Co films were made by DC sputtering and the covered by thermal evaporated 8nm Al/AlOx. Temperature dependent resistances were measured using four probe technique in low temperature system. Data can be well described by combination of the electron-electron interaction mechanism and the parallel connection model. Hence, we believe that the covering layer (Al/AlOx) does not affect the electrical transport in the two dimensional magnetic Co layer.
For most magnetic materials, inverse MR occur when current is applied along magnetic field direction and normal MR occur when current is applied perpendicular to field direction. This scenario can be attributed to the s-d scattering effect is usually referred as anisotropic magneto-resistance (AMR). In a very thin magnetic film, surface oxidation can become very severe and affect its intrinsic properties. Here, we have performed low temperature magneto-resistance and magnetization measurements for a series of Co thin film with different degrees of oxidation to investigate the role of surface oxidation. For thicker films and thin films with less oxidation, magneto-transports behave as theoretical expectation described above. However, for thin films with severe oxidation, the magneto-transports are completely reversed. The inverse MR is replaced by normal MR when current is applied along magnetic field direction. The normal MR is changed to inverse MR when current is applied perpendicular to field direction. It has been known that CoO is an antiferromagnetic material. Hence we suggest that there are two possible reasons for such reversed behaviors in MR. One is the magnetic domains change due to the ferromagnetic/antiferromagnetic coupling and the other is asymmetric density of state change due to the additional interfacial scatterings to CoO.
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