High-frequency magnetic properties in metal-nonmetal granular films

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 rho of 500-1000 mu Omega 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. (C) 1996 American Institute of Physics.