Rotatable Anisotropy in Thin Permalloy Films

Films which possess rotatable anisotropy have been observed. In these films, the easy direction of magnetization can be selected by the application of a sufficiently large magnetic field. The temperature dependence of hysteresis and resistivity have been studied. Films have also been examined by electron diffraction combined with partial etch techniques. It is concluded that a nickel oxide layer on the surface of the film is essential for the existence of rotatable anisotropy. Some mechanisms that may be responsible for this phenomenon are discussed.