High-frequency magnetic properties in metal–nonmetal granular films (invited)

Abstract

The structure and properties of Co–N and Co–O based films, prepared by rf magnetron reactive sputtering using nitrogen or oxygen and argon gases, have been studied. Transmission electron microscopy (TEM) observation reveals that each Co–(Al or Si)–(N or O) film is a typical film with granular structure, with grain size less than 5 nm. It is found by micro‐focused energy‐dispersive x‐ray and electron energy loss spectroscopy analysis that the grains are mainly composed of Co and the intergranular regions are ceramics of N or O. In Co–N based films, soft magnetic properties are found in both Si and Al containing films over a wide range of film preparation conditions and compositions. Only the films with Al show soft magnetic properties in Co–O based films, which have ρ of 500–1000 μΩ cm, H_k of about 80 Oe and B_s of about 10 kG. By adding about 10 at. % Pd, the soft magnetic properties and H_k of Co–O based films are significantly improved, with H_k more than 180 Oe. These films exhibit a remarkable constant frequency response of the permeability up to around 500 MHz, which is approximately explained by the Landau–Lifshitz formula.