XVII Symposium on Condensed Matter Physics - SFKM 2007, Vršac - Serbia Metallic nanoparticles embedded in an insulator matrix: growth mechanisms, magnetic and transport properties Z. Konstantinović 1,* , M. García del Muro 1 , M. Varela 2 , X. Batlle 1 and A. Labarta 1 1 Dpt de Física Fonamental, UB, Martí i Franquès 1, 08028 Barcelona, Spain 2 Dpt de Física Aplicada i Òptica, UB, Martí i Franquès 1, 08028 Barcelona, Spain Abstract. Granular thin films constituted of metallic particles (Ag, Co, Au) embedded into a dielectric matrix (ZrO 2 ) were grown by pulsed laser deposition (PLD) in a wide range of metal volume concentrations x. Transmission electron microscopy (TEM) shows regular distribution of mostly spherical crystalline metal particles with sharp interface with the amorphous matrix. Two mechanisms of particle growth are observed, giving rise to very different values of particle sizes and percolation thresholds. The mean particle size and width of distribution extracted from direct TEM observation and compared to the values obtained by fitting the low field magnetic susceptibility and isothermal magnetization of Co particles in the paramagnetic regime to a distribution of Langevin functions. The dc transport in the dielectric regime is well described in terms of thermally assisted tunneling. The ac transport shows a complex low-frequency absorption phenomenon, directly related with the observed nanostructure. INTRODUCTION Granular films constituted of metallic particles embedded into a dielectric matrix [1], comprise a very active research due to their relevant basic properties and potential applications [2]. When particles are reduced to nanometric size their properties are different from those of the bulk state, arising a wide variety of new phenomena, such as finite-size and surface effects, interparticle interactions, and enhanced properties. In order to properly correlate the observed behavior with the corresponding nanostructure and to accurately compare with the theoretical predictions, the experimental model system should contain a narrow size distribution of immiscible nanoparticles very well defined with respect to the matrix. Recent works demonstrate that pulsed laser deposition (PLD) produces granular thin films that are very close to this nanostructured ideal model. In this paper, we concentrate on the structural, transport and magnetic properties of Ag, Co and Au particles embedded in ZrO 2 matrix grown by PLD with the same metal volume concentration x=0.23. * Present address: Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus Universitari de Bellaterra, 08193 Bellaterra, Spain, mail: zorica@icmab.es 1