HDR

Lundi 8 Décembre 2014 à 14h00.

Magnetic and Spintronic Properties of Cluster-Assembled Nanostructures

''Cluster-assembled nanostructures are fabricated by co-depositing pre-formed metal clusters onto a substrate together with a protective and stable matrix. Here we discuss experimental studies of the magnetic and spintronic properties of cobalt nanoparticles of varying size and embedded in different solid matrices. The improved data treatment technique developed at the ILM and termed “triple fit” gives, together with its extensions, access to highly reliable values for the magnetic diameter distribution and the magnetic anisotropy, including possible biaxial terms. This technique is used to study interface effects and to study size-dependent variations of the magnetic anisotropy of embedded cobalt clusters. The latter are rationalized in the frame of two models as being due to shape and surface influences. The Giant Magnetoresistance response of granular media is then studied in well-defined and characterized cluster-assembled nanostructures. The theoretical model developed by Zhang and Levy is used for a quantitative description and its limits are discussed. Lastly, a novel method for the improved detection of spin-dependent transport properties in granular media is presented. Here the derivative of the resistivity with respect to temperature suppresses the dominant part of the resistive signal and enhances all contributions which, through the temperature, depend on the external magnetic field.''