Berlin 2005 – scientific programme
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MA: Magnetismus
MA 32: Mikro- und nanostrukturierte magn. Materialien II
MA 32.1: Talk
Wednesday, March 9, 2005, 11:00–11:15, TU H1028
Anisotropy and Magnetic Microstructure of Monodisperse FePt Nanoparticles. — •Keir Foster1, Jörg Weißmüller1,2, Balaji Gopalan1, Harald Rösner1, and Joachim Kohlbrecher3 — 1Intititute for Nanotechnology, Forchungszentrum Karlsruhe, Postfach 3640, D 76021 Karlsruhe, Germany — 2Universität des Saarlandes, Im Stadtwald, PO Box 15 11 50, D 66041 Saarbruecken, Germany — 3Laboratory for Neutron Scattering, PSI, CH 5232, Villigen, Switzerland
The magnetic anisotropy and magnetic microstructure of 4nm fcc alloy FePt nanoparticles coated with an organic shell were investigated using small−angle neutron scattering (SANS). Measurements were performed in conjunction with more standard magnetic characterization techniques, including vibrating sample magnetometry and AC susceptibility. The average particle size and size distribution were determined from transmission electron microscopy and small−angle X−ray scattering. For a ferromagnetic material it is expected that the SANS scattering intensity varies as a function of the angle α between the magnetization vector M and the scattering vector q as sin2α. To enhance this magnetic component of the scattering, measurements were made with polarized neutrons. From the field dependence of the SANS cross−sections, above and below the superparamagnetic blocking temperature (TB), quantitative information about the magnitude and spatial variation of the magnetic anisotropy field perturbing the system and of the anisotropy of the individual particles themselves respectively is derived.