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MA: Fachverband Magnetismus
MA 39: Magnetic Particles
MA 39.5: Talk
Thursday, March 10, 2016, 10:30–10:45, H31
Ultra high magnetic anisotropy in octapod shaped iron oxide nanoparticles — •P Anil Kumar1,2, Gurvinder Singh3, Joachim Landers1, Giuseppe Muscas4,5, Davide Peddis5, Heiko Wende1, and Roland Mathieu2 — 1Faculty of Physics and CENIDE, University of Duisburg - Essen, Duisburg 47048, Germany — 2Department of Engineering Sciences, Uppsala University, 751 21 Uppsala, Sweden — 3Department of Materials Science and Engineering, NTNU, N-7491, Trondheim, Norway — 4Department of Physics, Uppsala University, 751 21 Uppsala, Sweden — 5ISM-CNR, Area della Ricerca, C.P. 10-00016 Monterotondo Scalo, Roma, Italy
The shape of the magnetic nanoparticles is known to effect the magnetic anisotropy of the particles apart from the surface anisotropy. Here, we present results of macroscopic magnetic measurements and Mössbauer spectroscopy on octapod shaped Fe3O4 nanoparticles (of ∼ 20 nm size) obtained by controlling the growth of selective crystal orientations. These octapod particles show a distinct superparamagnetic transition indicative of a narrow size distribution. Interestingly, the isothermal magnetic hysteresis loops measured at 5 K and up to a field of 9 T are unconventional of any iron oxide system. The hysteresis loop remains open and the magnetization is unsaturated even up to 9 T field, indicating a very high magnetic anisotropy of these particles. Temperature dependent and in-field Mössbauer spectroscopy analysis also supports the inferences drawn from the macroscopic magnetic measurements. We will discuss possible reasons for such a high magnetic anisotropy in these particles.