Regensburg 2010 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 9: Magnetic Particles, Clusters
MA 9.1: Vortrag
Montag, 22. März 2010, 15:15–15:30, H23
Magnetic properties of NiO nanoparticles investigated by SQUID and magnetic Raman scattering — •Farrakh Shahzad1, Peter Knoll1, Karl Ettinger2, Kashif Nadeem1, Heinz Krenn1, Gabor Kozma4, Akos Kukovecz4, Zoltan Konya4, Ilse Letofsky-papst3, Karin Pressl1, and Petra Granitzer1 — 1Institute of Physics , Karl-Franzens University, graz, austria — 2institute of earth sciences, karl-franzens university, Graz, Austria — 3Technical University, Graz, Austria — 4Department of applied and environmental chemistry, University of Szeged, Hungary
We have measured the magnetization of NiO Nanoparticles with sizes ranging from 4nm-85nm by SQUID magnetometer. The Nanoparticles were prepared by Sol-gel and ball milling techniques. However, these measurements are very sensitive to induced small magnetic moments but do not directly measure the anti-ferromagnetic ordered spin pairs. This can be done by magnetic Raman scattering. Temperature-dependent magnetic Raman spectra for NiO single crystal are well known and understood, in which two-magnon peak (2M) is due to the anti-ferromagnetic nature of this material. In our measurements for Nanoparticles of diameter 40nm, 2M peak is not present at room temperature but appears at certain lower temperature range and then again disappears at very low temperature. For Nanoparticles of diameter 85nm, this peak is present at room temperature but still not present at very low temperature. 2M peak is not observed at any temperature for particles having diameter less than 40nm. These new experimental results will be presented within the so for established models.