Formation of non-equilibrium Fe-Au solid solutions in nanoclusters

Fe-Au nanoclusters ranging in composition from ∼33 to 79 at. % Fe were prepared by inert gas condensation. Resulting phases were single crystalline solid solutions for all compositions with significant defects present. The as-deposited clusters formed in a bcc structure for Fe content >65 at. % and in a fcc structure for Fe < 65 at. %. Lattice parameters were expanded beyond rule-of-mixture estimates. The lattice expansion is explained by an analytical self-interstitial model. All clusters were ferromagnetic, although the fcc structures showed low magnetization. The low magnetizations are thought to arise from antiferromagnetic cores with uncompensated ferromagnetic surface spins.