Soft magnetic properties of NiFe-Ru thin films and their application to biasing films in magnetoresistive elements

The effects of the addition of Ru on the magnetic properties of permalloy thin films have been investigated. The alloy composition was (Ni81Fe19)(1-x)Ru-x; the films were sputtered onto glass substrates at temperatures between room temperature and 200 degrees C. The saturation magnetization, coercivity, and anisotropy field decrease with increasing Ru content. The electrical resistivity initially increases rapidly with increasing Ru content, then saturates at approximately 6% Ru, at a value of approximately 90 x 10(-8) Omega m. Although the magnetoresistance change (Delta rho) does not decrease, the magnetoresistivity (Delta rho/rho) decreases with increasing Ru content due to increased resistivity (rho). The magnetostriction moves from minus to plus with increasing Ru content and reaches nearly zero at 6% Ru. Fabricated magnetoresistive heads with the (NiFe)-Ru/Ta/NiFe structure show high output and noiseless wave forms.