Structural, Magnetic, and Transport Properties of Fe(1-x)Rh(x)/MgO(001) Films Grown by Molecular-Beam Epitaxy

Fe(1-x)Rh(x) layers are grown with varying rhodium fraction x on (001)-oriented MgO substrates by molecular-beam epitaxy. Film structural, morphological, magnetic, and transport properties are investigated. At room temperature, layers are ferromagnetic (FM) for x ≤ 0.48 and antiferromagnetic (AF) for x > 0.48. Separating the two magnetically ordered phases at x = 0.48 is an abrupt change in the Fe(1-x)Rh(x) lattice parameter of Δa = 0.0028 nm (Δa/a = −0.9%). For AF layers, the FM state is recovered by heating across a first-order phase transition. The transition leads to a large resistivity modulation, Δρ/ρ = 80%, over a narrow temperature range, ΔT = 3 K, in stoichiometric Fe(0.50)Rh(0.50)/MgO(001). The resistivity change is explained using a model based on independent spin conduction channels. For samples with compositions deviating from x = 0.50, fluctuations broaden ΔT and defect scattering reduces Δρ/ρ.