Magnetostriction and soft magnetic properties of (Co1−xFex)–Al–O granular films with high electrical resistivity

We have investigated the magnetic properties of $({\mathrm{Co}}_{\text{1−x}}{\mathrm{Fe}}_x\mathrm{)–}\mathrm{Al–O}$ granular thin films prepared by a reactive sputtering method in an atmosphere of ${\mathrm{O}}_{\mathrm{2}}\mathrm{+Ar}.$ The coercivity and electrical resistivity of the films are almost independent of x, but with increasing x the anisotropy field decreases linearly and the saturation induction has a broad maximum of 20 kG around $\text{x=0.7.}$ The granular films show the same general tendency as bulk Co–Fe alloys in the compositional dependence of magnetostriction (λ). The magnitude of λ varies with increasing annealing temperature. Using a film with $\text{x=0.08}$ as the core of a spiral-wound inductor gave a quality factor $\text{Q=25}$ at a frequency of 300 MHz.