Dresden 2014 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 9: Magnetic Nanoparticles

MA 9.5: Vortrag

Montag, 31. März 2014, 16:00–16:15, HSZ 401

Magnetic Anisotropy and relaxation of 24 single 43 nm Fe/Fe_xO_y core/shell-nanocubes — •Alexandra Terwey¹, Sabrina Masur¹, Ralf Meckenstock¹, Christian Derricks¹, Benjamin Zingsem¹, Florian Römer¹, Miguel Comensana-Hermo², and Michael Farle¹ — ¹AG Farle, Experimentalphysik, Universität Duisburg Essen, Germany — ²Centre de Recherche Paul Pascal, CNRS, Universite de Bordeaux, France

Due to their large surface contribution nano particles and small agglomerates hold unique magnetic properties distinguishing them from bulk or thin film material. Here, ferromagnetic resonance measurements of single 43nm edge length Fe/Fe_xO_y core/shell nanocubes are shown with full angle dependence. These measurements performed simultaneously on 22 of these nanocubes and on two dimers prove that the cubes show the same crystalline anisotropy field K₄/M=25mT which is surprisingly in the same range as that of bulk iron (28mT). SQUID measurements show a magnetization of M=2±0.5·10⁵A/m which is roughly 10% of the value of bulk iron. Considering a ferrimagnetic Fe_xO_y shell, d=7nm, the magnetization should be reduced to about 40%. This behaviour can be explained by an additional contribution such as shell anisotropy or a decrease of the magnetic moment at the internal interface. Furthermore, we find a small FMR linewidth of 4mT which corresponds to a damping of α=0.045 matching the linewidth of high quality epitaxial Fe films.