Berlin 2005 – wissenschaftliches Programm
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MA: Magnetismus
MA 20: Poster:Schichten(1-29),Spintrsp(30-45),Ex-Bias(46-63),Spindyn(64-75),Mikromat.(76-80),Cluster(81-94),Abbv.(95-99),Obflm(100-02),SpElek.(103-09),E-Theo(110-14),Mikromag.(115-16),Spin+PÜ(117-26),Mag.Mat.(127-51),Meth.(152-55),Mol.Mag(156-59),Kondo(160-65
MA 20.87: Poster
Montag, 7. März 2005, 14:00–18:00, Poster TU C
Jahn−Teller Effect in CuFe2O4 Nanoparticles — •Balaji Gopalan1, Jörg Weissmüller1,2, and Namdeo Gajbhiye3 — 1Institute for Nanotechnology, Forschungszentrum Karlsruhe, P. O. Box 3640, D-76021, Germany — 2Universität des Saarlandes, Fachrichtung Technische Physik, Saarbrücken, P.O. Box 151150, D-66041, Germany — 3Department of Chemistry, Indian Institute of Technology, Kanpur, 208016 India
Nanosize CuFe2O4 particles are prepared by coprecipitation method. The particles of various sizes are obtained by heat treatment at temperatures between 573−1273 K and are characterized by X−ray diffraction, Mössbauer spectroscopy and magnetization measurements. X−ray diffraction pattern indicates that the crystal structure of nanosize CuFe2O4 particles obtained above 973 K is tetragonal while that prepared below 973 K is cubic. The room temperature Mössbauer spectrum indicates that the isomer shift, quadrupole splitting and hyperfine field values are found to change with heat treatment temperature. These changes in Mössbauer parameters may also be due to the Jahn−Teller effect that essentially arises due to the migration of Cu2+ ions from tetrahedral sites to octahedral sites resulting in crystal structure change from cubic to tetragonal system. The maximum coercivity obtained has been 700 Oe at heating temperature of 823 K. The enhanced coercive force can be mainly attributed to uniaxial magnetic anisotropy produced by crystal distortion.