Ordered phase formation in Sm-Co1−xCux and Er-Co1−xCux alloy films prepared on Cr(100) single-crystal underlayer

Abstract Sm 17 (Co 1− x Cu x ) 83 and Er 17 (Co 1− x Cu x ) 83 (at. %, x  = 0–1) alloy thin films are prepared on Cr(100) single-crystal underlayers at 500 °C by molecular beam epitaxy. The effect of Cu/Co composition on the ordered phase formation is investigated. Sm 17 (Co 1− x Cu x ) 83 (11 2 ¯ 0) films with hexagonal Sm(Co,Cu) 5 ( D 2 d ) ordered phase grow epitaxially on the underlayers for all the compositional range of x  = 0–1. On the contrary, the structure of Er 17 (Co 1− x Cu x ) 83 film varies depending on Cu composition. Amorphous phase is formed in the Er 17 Co 83 ( x  = 0) film. Er 17 (Co 1− x Cu x ) 83 (11 2 ¯ 0) epitaxial films with Er(Co,Cu) 5 ( D 2 d ) ordered phase are obtained for the compositional range of x  = 0.25–0.5. With further increasing the x value, the crystallographic phase varies to a phase other than D 2 d . Partial substitution of the Co sites in ErCo 5 structure with Cu atoms and control of the amount of Cu atom are important to stabilize the Er(Co,Cu) 5 phase.