Texture formation in epitaxial hard magnetic Sm2Co7 thin films

Abstract

AbstractThe crystallographic and magnetic texture of epitaxial, hard magnetic Sm2Co7 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), Sm2Co7 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 Sm2Co7 crystals have a 45° and 60° orientation to the substrate plane. The volume fraction of the tilted orientations decreases with decrease in the Sm2Co7 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(011) substrate Sm2Co7 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.