High frequency measurement of thin film magnetoresistance

A system to measure the high frequency MR curve of thin films was developed . Two problems had to be solved to realize MR measurement at frequencies ab ove several MHz, namely, to produce a high amplitude magnetic field and to develop electrodes less sensitive to inductive high frequency noises than t he conventional four probe electrodes. These problems were solved by making use of the resonance of a coil with a ferrite core connected in parallel w ith to a capacitor, and by contacting patterned thin film electrodes to the sample surface with a suitable pressure. The result was an appreciable red uction of inductive noises. Using the resonance circuit and electrodes we c ould obtain AMR curves of Permalloy films at frequencies up to 1.8 MHz in a field of 110 Oe pp.