Magnetoresistance and Strain in Permalloy Films

We measured the magnetoresistance (MR) of sputtered Permalloy (Ni_(83)Fe_(17)) films with external strains produced by piezoelectric transducer actuators. We observe that the MR ratio was increased by 2.3 times by a compressive strain of 3.5×10-⁴ compared to that of the as-deposited film. Tensile strains and compressive strains reduced the MR ratio. These observations suggest that it is possible to tune the MR properties through the use of the external strains. We expect to apply the results for the multi-head magnetic recorders with selectively activated recording heads.