AVS 49th International Symposium
    Magnetic Interfaces and Nanostructures Monday Sessions
       Session MI+NS-MoA

Paper MI+NS-MoA6
Study of the Magnetic Cluster/Superconductiviting Matrix Interface: the Co/Nb System

Monday, November 4, 2002, 3:40 pm, Room C-205

Session: Self-Assembly and Nanomagnetism
Presenter: V. Dupuis, DPM Lyon - France
Authors: V. Dupuis, DPM Lyon - France
L. Favre, DPM Lyon - France
M. Jamet, DPM Lyon - France
J. Tuaillon-Combes, DPM Lyon - France
P. Melinon, DPM Lyon - France
A. Perez, DPM Lyon - France
Correspondent: Click to Email
Thin films consisting on pure Co nanoparticles embedded in a Nb superconducting matrix have been prepared from clusters preformed in the gas phase using the Low Energy Cluster Beam Deposition (LECBD) technique.@footnote 1@ Such films are subsequently e-beam lithographied in view to prepare ultrahigh sensitivity Micro-SQUID magnetometer devices and to study the magnetization reversal mechanism of an individual nanocluster.@footnote 2@ X-ray characterization experiments and Transmission Electron Microscopy performed on an assembly of cobalt clusters embedded in a niobium matrix have shown that such nanogranular films consist on crystallized fcc Co-grains in the form of 3 nm-diameter truncated octahedron (~ 1000 Co-atoms) randomly distributed in the polycrystalline niobium matrix. Sites of Co-atoms in the cluster core and at the cluster-matrix interface have been evidenced showing an alloyed Co-Nb interface concerned by almost one monolayer. On another hand, VSM magnetization measurements performed in the superparamagnetic regime evidenced a magnetic size of the Co-clusters lower than the one as deduced from TEM observations. So, in-situ complementary measurements under synchrotron radiation performed on Co/Nb bilayers grown in UHV confirm the presence of an alloyed Co@sub 6@Nb@sub 7@ interface which acts as a magnetically dead layer. Finally, from micro-SQUID measurements performed at 35 mK on one individual Co-cluster, we obtained a 3D-astroid shape corresponding to second order bi-axial anisotropy terms which can be attributed to surface anisotropy contributions ("Néel" model) underlying the main interfacial contribution in such nano-object. @FootnoteText@ @footnote 1@ A. Perez et al. Materials Transactions, Special Issue on Nano-Metals 1, 42,1460 (2001). @footnote 2@ M. Jamet et al. Phys. Rev. Lett., 86, 4676 (2001).