抄録
The polar Kerr magnetooptical effect has been used as the main method to measure the magnetization characteristics of films with perpendicular magnetic anisotropy. The author found, however, that on some occasions the shape of the polar Kerr loop as well as the Hall loop changed remarkably (or drastically in some cases) with the orientation of the sample in the investigation of rare earth-transition metal alloy amorphous films. This is due to the cooperative effect of the in-plane or oblique component of magnetization in the sample film and the imperfect perpendicularity of the magnetic field in the polar Kerr apparatus. There is a possibility that such an effect leads to serious errors and misunderstanding in the measurement of perpendicular anisotropy films containing in-plane magnetic component, because some degree of deviation of field from the film normal is unavoidable in actual polar Kerr systems. Therefore, it is very important to examine the perpendicularity of the magnetic field of the magnet in the polar Kerr system before the experiment. However, it is difficult to measure the deviation angle of magnetic field by the ordinary techniques. This paper presents an original method to measure the perpendicularity of the magnetic field using an evaporated nickel thin film with oblique uniaxial magnetic anisotropy. In this method, the deviation angle of field can be obtained from the ratio of the maximum coercivity to the minimum one of the Hall or Kerr loop when the Ni film is rotated on the sample stage.
