Magnetoresistance and Magnetic Switching in Permalloy Films

Magnetoresistance measurements have been used to study the magnetic properties of Permalloy films. Resistivities parallel and transverse to the current were measured simultaneously as the applied magnetic field was varied in magnitude or direction in the film plane. The results are discussed in terms of a representation in which the resistivity components are regarded as Cartesian coordinates. This representation is independent of the current direction relative to any magnetically preferred orientations in the film. The statistical,domain-wall, switching model of Conger and Essig is extended to include the situation in which the field and easy magnetic axis are not parallel, and a switching profile is constructed which gives a unified representation of the domain wall and coherent rotational switching response of a uniaxial film to an applied field. The incidence of moving domain walls under certain field conditions is discussed with the help of this profile,and it is shown that the magnetoresistance curves may be understood in terms of the magnetic changes.