Formation of Sm(Co_1–xNi_x)₅ epitaxial thin films on Cu(111) underlayers

¹ Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551, Japan
² Graduate School of Fine Arts, Tokyo University of the Arts, 12-8 Ueno-koen, Taito-ku, Tokyo 110-8714, Japan

^a Corresponding author: m-yamada@futamoto.elect.chuo-u.ac.jp

Published online: 3 July 2014

Abstract

Sm₁₇(Co_1–xNi_x)₈₃ (at. %, x = 0, 0.2, 0.8, 1) alloy thin films are prepared on Cu(111) underlayers hetero-epitaxially grown on MgO(111) substrates by molecular beam epitaxy. The effects of substrate temperature and Ni/Co composition on the growth behavior and the detailed resulting film structure are investigated. Formation of RT₅ ordered phase is enhanced with increasing the substrate temperature and the Ni composition. The long-range order degrees of Sm₁₇Co₈₃, Sm₁₇(Co_0.8Ni_0.2)₈₃, Sm₁₇(Co_0.2Ni_0.8)₈₃, and Sm₁₇Ni₈₃ films deposited at 500 °C are estimated to be 0.77, 0.82, 0.89, and 0.97, respectively. The Sm₁₇(Co_1–xNi_x)₈₃ films with RT₅ structure consist of two types of epitaxial (0001) variant whose orientations are rotated around the film normal by 30° each other. With increasing the Ni content ratio of x from 0 to 1, the volume ratio of two variants is varied from 53:47 to 94:6. The nucleation of only one-type variant with a smaller lattice mismatch with respect to Cu underlayer is promoted with increasing the Ni content ratio.