Synthesis and Properties of Magnetic Cobalt–Samarium Nanocluster Assemblies

Bimetallic cobalt–samarium nanoparticles are prepared in the gas phase using a combined laser vaporization-rare gas condensation source and subsequently deposited on various substrates or embedded in non-magnetic metallic matrix using the Low Energy Cluster Beam Deposition technique (LECBD). Structural and magnetic characterizations from assemblies of isolated clusters, reveal Co – Sm clusters with a mean diameter around 3.5 nm, and a loss of magnetization compared to the bulk SmCo 5 phase, probably due to an amorphous state associated to a segregation of the samarium atoms at the cluster surface. Annealing in ultra high vacuum up to 820 K considerably improves the crystallinity and the homogeneity of the mixed clusters leading to a significant increase of the magnetic anisotropy and consequently of the blocking temperature, as large as 400 K, without significantly increasing the mean size (around 6 nm). Such results seem promising for applications to high density memory devices and spintronics.