Gd and Tb nanoparticles were obtained via annealing of sputtered multilayer precursors. Detailed structural examination, involving energy-filtered imaging and high-resolution electron microscopy along with transmission electron microscopy and scanning electron microscopy techniques, revealed an island structure for the rare earths within the precursors, which further develops to nanoparticles upon annealing. A dramatic change in the magnetic characteristics of the nanoparticles is observed comparing to the bulk. Magnetic data are discussed to distinguish between true size effects and superparamagnetism. The obtained results give a credit to the former scenario.

• Received 25 March 2002

DOI:https://doi.org/10.1103/PhysRevB.67.054403