MAGNETIC-PROPERTIES OF NANOSTRUCTURED THIN-FILMS OF TRANSITION-METAL OBTAINED BY LOW-ENERGY CLUSTER BEAM DEPOSITION

Clusters of iron, cobalt, and nickel are produced in a laser vaporizat ion source. The size distributions of the incident clusters are checke d by time-of-flight mass spectrometry before deposition at low energy. Studying the near threshold photoionization, Co-n and Ni-n clusters e xhibit an icosahedral structure while for iron, no clear structure eme rges. Neutral clusters were deposited on different substrates at room temperature with thicknesses up to 100 nm in view to determine their s tructure and magnetic properties. A limited coalescence of the cluster s is observed from high-resolution transmission electron microscopy. N o icosahedron has been observed but cuboctahedron and interface twins between adjacent particles have been clearly identified in Ni films. G razing incidence x-ray diffraction experiments reveal a classical phas e with grain size around 6 and 4 nm for Fe and Ni films, respectively but an anomalous fee phase for Co films and a very low grain size of 2 nm. The density of films determined by x-ray reflectivity was estimat ed to represent only 60%-65% of the bulk density. Magnetic behaviors s tudied by ferromagnetic resonance and SQUID magnetization measurements have been interpreted using the correlated spin glass model. Mossbaue r spectra performed on Fe films at zero field revealed the presence of 20% of iron in the form of thin nonmagnetic oxide skin surrounding Fe grains which allow to find 2.2 mu(B) per magnetic iron atom in agreem ent with macroscopic magnetic measurements. Nevertheless we found an a nomalous reduced atomic moment for Ni film.