Dresden 2014 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 34: Poster Session

MM 34.23: Poster

Tuesday, April 1, 2014, 18:00–20:00, P4

TEM investigation of segregation phenomena in Nd-Fe-B nanoparticles — •Frank Schmidt^1,2, Darius Pohl¹, Ludwig Schultz¹, and Bernd Rellinghaus¹ — ¹IFW Dresden, Helmholtzstr. 20, D-01069 Dresden, Germany — ²TU Dresden, IFWW, D-01062 Dresden, Germany

Nd₂Fe₁₄B is a comparably hard magnetic phase as L1₀-ordered FePt, however, with a smaller Curie temperature. Therefore, Nd₂Fe₁₄B nanomagnets could be an interesting materials alternative the widely discussed L1₀-FePt in HAMR media. There are different methods to synthesize Nd₂Fe₁₄B nanoparticles, such as chemical methods or surfactant-assisted ball milling.

The purpose of this study is to investigate free Nd-Fe-B nanoparticles prepared by inert gas condensation and how different thermodynamic conditions affect them. In-flight optical annealing of the nanoparticles allows to compare unheated particles with heated particles, which are assumed to be closer to the thermally equilibrated state. Transmission electron microscopy was used to determine the atomic structure and chemical composition of the particles. Unheated particles are found to be mainly amorphous, while rapidly optically annealed particles are crystalline. We observe both a Nd enrichment in the shell and a Fe enrichment in the core of the differently treated particles. This segregation is more pronounced for heated particles, where a clear core-shell structure is formed that can be explained by a reduction of the surface energy.