Magnetic Properties of Co Thin Films Fabricated by Thermal Heating under Vacuum

Abstract

We used thermal heating process, under a pressure of 10−7 mbar, to fabricate thin films of cobalt on monocrystalline silicon Si (100) substrates. The incident beam strikes the substrates under normal and oblique incidences within a home-made evaporation chamber. The thickness of the deposited films ranges from 18 to 400 nm. Microscopic characterizations of the films are performed with X-ray diffraction (XRD) measurements and infer that all the samples are polycrystalline, with a hexagonal close packed (h.c.p.) structure and exhibit a preferred orientation, for the perpendicularly evaporated films. The grain size is found to increase with the thickness of the magnetic layer. The values of the computed parameters allow concluding to a compressive stress for the thinnest films. The static magnetic properties have been performed by means of magnetic force microscopy (M.F.M.) and Alternating Gradient Field Magnetometer (A.G.F.M.) tools. The dynamic magnetic properties have been investigated using Brillouin Light Scattering (B.L.S.) measurements. The MFM observations were performed after in-plane ac demagnetization, and stripe patterns are observed, only for the thickest films, showing the weaker perpendicular anisotropies. We used the findings provided by these tools to compute the effective magnetic anisotropy factors K u . Values of K u , higher than 13 × 106 erg.cm−3, have been found.