Ferromagnetism in DyRh and DyRhX (X = Fe, Ni, Co, Gd) thin films

Abstract

In an effort to achieve large high-field magnetization and increased Curie temperature, polycrystalline DyRh, (DyRh)95X5 and (DyRh)85X15 (X = Fe, Co, Ni, Gd) thin films have been prepared via ultra-high vacuum dc co-sputtering on SiO2 and Si wafers, using Ta as seed and cap material. A body-centred cubic CsCl-like crystal formation (B2 phase) was achieved for DyRh around the equiatomic equilibrium, known from single crystals. The maximum in-plane spontaneous magnetization at T = 4 K in fields of µ0H = 5 T was found to be µ0MS,4K = (1.50 ± 0.09) T, with a ferromagnetic transition at TC = (5 ± 1)K and a coercivity of µ0HC,4K[D] = (0.010 ± 0.001)T (at T = 4 K) for layers deposited on substrates heated to 350 °C. Samples prepared at room temperature exhibited poorer texture, smaller grains and less B2-phase content; this did impact on the Curie temperature, which was higher compared to those layers with best crystallisation. However, the maximal magnetization remained unaffected. Ferromagnetic coupling was observed in ternary alloys of DyRhGd and DyRhNi with an increased Curie temperature, larger initial permeability and high-field magnetization, which was best for (DyRh)85Gd15 with µ0MS,4K[Gd15] = (2.10 ± 0.13) T. DyRhFe and DyRhCo showed antiparallel coupling of spontaneous magnetic moments.