Sputter gas pressure effects on the properties of Sm-Co thin films deposited from a single target

We grow epitaxial Sm-Co thin films by sputter deposition from an alloy target with a nominal SmCo5 composition on Cr(100)-buffered MgO(100) single-crystal substrates. By varying the Ar gas pressure, we can change the composition of the film from a SmCo5-like to a Sm2Co7-like phase. The composition, crystal structure, morphology and magnetic properties of these films have been determined using Rutherford Backscattering, X-ray diffraction and magnetization measurements. We find that the various properties are sensitive to the sputter background pressure in different ways. In particular, the lattice parameter changes in a continuous way, the coercive fields vary continuously with a maximum value of 3.3 T, but the saturation magnetization peaks when the lattice parameter is close to that of Sm2Co7. Moreover, we find that the Sm content of the films is higher than expected from the expected stoichiometry.