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MA: Magnetismus
MA 32: Magnetic Particles / Clusters
MA 32.10: Vortrag
Donnerstag, 30. März 2006, 17:30–17:45, HSZ 401
Charge Transfer Controlled Magnetism of FePt Nanoparticles — •Balaji Gopalan1, Christophe Stroh1, Keir Foster1, Christian Lemier1, Raghavan Viswanath1, Jörg Weißmüller1,2, and Stefan Mangold3 — 1Institut für Nanotechnologie, Forschungszentrum Karlsruhe GmbH, Hermann-von-Helmholtz-Platz 1, D-76344 Eggenstein-Leopoldshafen, Germany — 2Fachrichtung Technische Physik, Universität des Saarlandes, 66041 Saarbrücken, Germany — 3Institut für Synchrotronstrahlung, Forschungszentrum Karlsruhe GmbH, Hermann-von-Helmholtz-Platz 1, D-76344 Eggenstein-Leopoldshafen, Germany
The effect of charge transfer between ligand and nanoparticles on the magnetic properties of monodispersed 2.0 nm FePt nanoparticles is studied. For this purpose, we have synthesized FePt nanoparticles covered by high fatty acid ligand (FePtCL), octadecanethiol (FePtSH), and oleic acid/oleylamine mixture (FePtOAc) as a series and the magnetic properties are compared. The superparamagnetic blocking temperature (TB) are found to be 14, 11 and 7.5 K for FePtCL, FePtSH and FePtOAC samples respectively. The coercivity (Hc) values measured at 5 K are 3880, 4800 and 4000 Oe for FePtCL, FePtSH, and FePtOAC respectively. These differences suggest that the effective magnetic anisotropy constant (Keff) is different for these samples. XANES Fe K pre-edge values of 7114.6 and 7115.4 eV are observed for FePtCL and FePtSH (reference Fe value is 7112.1 eV) indicating that Fe in 2(+) and 3(+) oxidation states respectively in these samples. A correlation between the observed oxidation states and the magnetic properties will be attempted.