Berlin 2015 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 38: Magnetic Nanoparticles
MA 38.5: Vortrag
Donnerstag, 19. März 2015, 10:30–10:45, H 0110
The effect of segregation on the magnetic properties of RE-TM nanoparticles — •Frank Schmidt1,2, Darius Pohl1, Ludwig Schultz1, and Bernd Rellinghaus1 — 1IFW Dresden, Helmholtzstraße 20, D-01069 Dresden, Germany. — 2TU Dresden, IFWW, D-01062 Dresden, Germany.
Rare earth transition metal compounds like Nd2Fe14B or SmCo5 are among the magnets with the highest energy product and coercive field. Nonetheless, there is still demand further to improve the magnetic properties of these alloys. The present study reveals the investigation on the formation and phase stability of RE-TM nanoparticles from the gas phase which could serve as a model system for their bulk counterparts. Particular attention is paid to the question, if the intermetallic Nd2Fe14B and SmCo5 phase form in particles with only a few nanometers in size, which grow without contact to any solid or liquid matrix in a low pressure Ar atmosphere. It also addresses the possibility of segregation that goes along with the phase formation and how this possibly affect the magnetic properties. Aberration-corrected transmission electron microscopy was used in combination with spectroscopic methods to determine the local atomic structure and the chemical composition, and it was found that in both cases, the RE element segregates to the particle surface. The magnetic properties of Nd-Fe-B and Sm-Co nanoparticles ensembles as determined from VSM measurements are correlated with the resulting core-shell structure of these RE-TM particles.