Preparation and properties of coevaporated amorphous Co-Zr thin films

Abstract

Co1-xZrx thin films (5<x<35) were prepared by coevaporation in a two E-beam source system on glass substrates held at 30°C. The crystallinity of all films were monitored by x-ray diffraction techniques; the films in the composition range x≥7.4 were found to be amorphous. Magnetization, hysteresis loop, and FMR measurements were carried out with these Co-Zr films. The saturation magnetization as a function of composition shows similar trends as in the Co-Ti thin films. The FMR spectra were rather complex with four to six modes for perpendicular resonance; the most intense mode gives a value for 4πMs close to the static data. The other modes at higher resonance fields may be caused by preferential oxidation of Zr or a large negative anisotropy induced by oxidation. Auger and ion probe profile analysis of the Co-Zr films indicated the presence of oxygen throughout the bulk of these films. SEM examination of some of these Co-Zr films showed the existence of a columnar structure, and it is possible that oxygen transport is enhanced along the column boundaries. Regions with varying degrees of oxidation are thought to be responsible for the multiple FMR modes.