Thickness dependent magnetic and structural properties of Co(x)Cr(1-x) thin films evaporated on Si(100) and glass substrates.

Series of Co(x)Cr(1-x) thin films have been prepared by thermal evaporation onto Si(100) and Corning glass substrates, x ranging from 1 to 0.60, and the magnetic layer thickness from 17 to 220 nm. The dependence of the magnetic and crystallographic properties on the thickness of CoCr layers have been investigated. The chromium content effect on the saturation magnetization of the films has also been examined. Microscopic characterizations of the films, performed with X-ray diffraction (XRD) measurements, infer that all the samples are composed of hcp phase crystallites with good orientation of the c axis showing a (0001) preferred orientation. The grain size increases with thickness. Atomic force microscopy (AFM) observations show very smooth film surfaces, the highest rms value being 18 amgstroms. The saturation magnetization M(s) was found to decrease from 1400 emu/cm3 to a few emu/cm3 as x decreases from 1 to 0.60, for all values of the thickness. In-plane squareness up to S = 0.83 has been observed for the CoCr/Si thinnest film, and S = 0.90 for the Co/Si thinnest film, too. Magnetic Force Microscopy (MFM) study points out the absence of stripe domains equilibrium magnetization structure for the CoCr thin films whereas the thick Co films present a well defined stripe pattern. From the magnetocrystalline anisotropy field H(a) values extracted from the fit of the BLS spectra, we have computed effective magnetic anisotropy factors K(u), as well. Their negative values for the CoCr samples confirm an in-plane magnetic anisotropy for the thin film magnetization.