Berlin 2015 – scientific programme

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MA: Fachverband Magnetismus

MA 38: Magnetic Nanoparticles

MA 38.5: Talk

Thursday, March 19, 2015, 10:30–10:45, H 0110

The effect of segregation on the magnetic properties of RE-TM nanoparticles — •Frank Schmidt^1,2, 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.