Texture formation in epitaxial hard magnetic Sm2 Co7 thin films

The crystallographic and magnetic texture of epitaxial, hard magnetic Sm 2 Co 7 films prepared on Cr-buffered MgO single-crystal substrates are analyzed. Substrate symmetry, deposition temperature, and deposition rate are systematically varied, resulting in a variety of different, but epitaxial orientations. On Cr-buffered MgO(001), Sm 2 Co 7 grows with three different types of orientations: one inplane orientation with the c-axis aligned in the substrate plane parallel to MgO[100] and [010], and two tilted orientations, where the c-axes of the Sm 2 Co 7 crystals have a 45° and 60° orientation to the substrate plane. The volume fraction of the tilted orientations decreases with decrease in the Sm 2 Co 7 deposition temperature. A lower limit is given by the epitaxial growth temperature, which is necessary to form a fully crystalline, epitaxial film. This temperature can be reduced by lowering the deposition rate. Thus, almost completely inplane aligned films can be achieved by a low-rate/low-temperature deposition. On a Cr-buffered MgO(01 1) substrate Sm 2 Co 7 grows with a single orientation, i.e., with the c-axis aligned onto the substrate plane parallel to MgO[100]. The findings are discussed considering elastic strain minimization, thermodynamics and kinetics of film growth, surface faceting, and Co-particle formation.