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MA: Fachverband Magnetismus

MA 12: FS: Single Nanomagnets

MA 12.4: Topical Talk

Dienstag, 23. März 2010, 12:15–12:45, H22

Exploring single nanomagnets with photoelectron microscopy — •Florian Kronast — Helmholtz-Zentrum Berlin GmbH, Albert-Einstein-Str. 15, D-12489 Berlin, Germany

Nanostructures exhibit new and interesting magnetic properties that can not be derived from bulk properties. E.g. their effective magnetization and the Curie temperature may differ dramatically from bulk values due to finite size effects. Magnetic nanoparticles with core-shell structures are likely to show different magnetic order at the surface and in the core. In ensembles of nanoparticles inter-particle interactions strongly influence their individual magnetic properties. To resolve those nanoscale effects on the appropriate length scale we investigate individual nanomagnets by means of microspectroscopy. Using photoelectron microscopy with synchrotron light excitation we can access their chemical composition, magnetic moment and orientation with 30nm lateral resolution. A built-in magnetic yoke and temperature control allows us to measure magnetic responses of individual nanoparticles to an external magnetic field of up to ± 50mT as a function of temperature. To correlate magnetic properties of individual nanomagnets with their size, chemical composition, structure, and local coordination we combine our microspectroscopy data with detailed structural information obtained by high resolution electron microscopy. Measurements on Fe nanoparticles with a cubic shape and a side length 18nm [1] demonstrate how strongly their magnetic properties vary with their local coordination and oxidation state. [1] A. Shavel et al, Adv. Funct. Mat. 17 (2007) 3870