| Magnetic properties of materials have been discovered since three thousand years ago and have been widely used in industry and our daily life such as magnetic cores in electric transformers, giant magnetic resistance (GMR) in recording devices and so on. For the study of magnetic materials, magnetization, Curie temperature, and magnetic anisotropy are basic parameters, in which magnetic anisotropy is especially important for the magnetic recording materials. In this thesis, the method of transport measurement is applied to study the magnetic anisotropy in magnetic films.(1) We measured the planar Hall effect of magnetic films with the transport measurement device, from which magnetic anisotropy was obtained. Then we compared this anisotropy with the one measured by Rot MOKE and found that they coincide with each other very well, which proves the reliability of studying the magnetic anisotropy with the transport measurement method.(2) We measured the magnetic anisotropy changes with varying temperatures in Fe/CoO ferro-antiferromagnetic layers with the transport measurement method. It was found that a large uniaxial anisotropy Hku was produced in Fe/CoO system under low temperatures and this Hku decreased gradually with increasing temperatures and finally disappeared with temperatures above the CoO Neel temperature. In addition, the easy axes of this uniaxial anisotropy was always in the direction of [110] or [110] of CoO and has the same Hku value, independent of magnetic cooling directions. We conclude that it is Fe/CoO ferro-antiferromagnetic coupling that results in the large uniaxial anisotropy and the large four-fold anisotropy of CoO determines the easy axes can only be in the [110]or [110] direction of CoO. The exchange coupling also induces a 4-fold anisotropy with the easy axis along CoO<100> directions. |
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