Structural and magnetic properties of epitaxial Mn–Ge films grown on Ir/Cr buffered MgO(0 0 1)

Epitaxial Mn–Ge films with varying composition have been prepared on Ir/Cr buffered MgO(0 0 1) substrates using DC magnetron sputtering. The effect of composition on phase formation, texture and magnetic properties of Mn–Ge films has been investigated. These films grow epitaxially on Ir/Cr buffered MgO(0 0 1) with a tetragonal D022 type structure. From the pole figure analysis the epitaxial relationship is determined to be: D022 Mn–Ge [1 0 0] (0 0 1)||Ir [1 0 0] (0 0 1)||Cr [1 1 0] (0 0 1)||MgO [1 0 0] (0 0 1). Mn–Ge films close to stoichiometric composition (Mn77.5Ge22.5) exhibit perpendicular magnetic anisotropy with crystallographic c-axis being the easy axis of magnetization. The room temperature measured values of coercivity µ 0 H c, saturation magnetization M S and anisotropy field µ 0 H A for Mn77.5Ge22.5 are 2.86 T, 90 kA m−1 and 9.6 T, respectively. Mn–Ge films with low and high Mn concentration possess high coercivity but extremely low magnetization and that can be ascribed to the presence of secondary phases of non-magnetic/low magnetic nature, possible interdiffusion, and especially partial substitution of excess Mn atoms into the Ge site.