title: Magnetic disorder in diluted FexM100-x granular thin films (M=Au, Ag, Cu; x < 10 at.%).
abstract: Nanogranular thin films of Fe7Au93, Fe7Ag93 and Fe9Cu91 have been sputtered onto Si(100) substrates with the aim of studying the magnetic interactions. X-ray diffraction shows a major noble metal matrix with broad peaks stemming from (111) textured fcc-Au, Ag and Cu. The noble metal forms a nanogranular environment, as confirmed by transmission electron microscopy, with mean particle sizes below 10 nm. The high magnetoresistance (>6%) reveals the existence of Fe nanoparticles. X-ray absorption near edge spectroscopy confirms the presence of a bcc-Fe atom arrangement and some dissolved Fe atoms in the matrix, and XMCD shows the polarization of Au by the Fe nanoparticles. DC-magnetization displays a field-dependent irreversibility produced by the freezing of magnetic nanoparticles into a superspin-glass state. The hysteresis loops remain unsaturated at 5 K and 45 kOe. The coercivity displays a sharp temperature decrease towards a minimum below 50 K, levelling off at higher values, reaching Hc = 200 Oe at 300 K. Annealing of FeAu results in a double-peak zero field cooled magnetization and a slight decrease of the coercivity. The interpretation of the results supports the presence of Fe nanoparticles embedded in the major noble matrix, with some diluted Fe atoms/clusters.
authors.affiliation: CITIMAC Unidad Asociada CSIC, Universidad de Cantabria, E-39005 Santander, Spain. diego.alba-venero@stfc.ac.uk
authors.forename: D
authors.initials: D
authors.lastname: Alba  Venero
authors.forename: L
authors.initials: L
authors.lastname: Fernández Barquín
authors.forename: J
authors.initials: J
authors.lastname: Alonso
authors.forename: M L
authors.initials: ML
authors.lastname: Fdez-Gubieda
authors.forename: L
authors.initials: L
authors.lastname: Rodríguez Fernández
authors.forename: R
authors.initials: R
authors.lastname: Boada
authors.forename: J
authors.initials: J
authors.lastname: Chaboy
mesh_terms: D003300:Copper / Q000737:chemistry*; D006046:Gold / Q000737:chemistry*; D058085:Iron Compounds / Q000737:chemistry*; D008280:Magnetics; D053768:Metal Nanoparticles / Q000737:chemistry*; D046529:Microscopy, Electron, Transmission; D036103:Nanotechnology; D012834:Silver / Q000737:chemistry*; D014961:X-Ray Diffraction
chemical_list: D058085:Iron Compounds; D012834:Silver; D006046:Gold; D003300:Copper