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MA: Fachverband Magnetismus

MA 52: Magnetic Thin Films III

MA 52.7: Vortrag

Donnerstag, 17. März 2011, 12:30–12:45, HSZ 403

Co₂FeGa Heusler nanoparticles at the interface of physics, chemistry and materials science. — •Changhai Wang, Frederick Casper, Benjamin Balke, Gerhard H. Fecher, and Claudia Felser — Institute of Inorganic and Analytical Chemistry, Johannes Gutenberg - University, 55099 Mainz

This work reports on the chemical synthesis and characterizations of the ternary Heusler Co₂FeGa nanoparticles. Specifically, the role of particle size in affecting the long and short range order and magnetic properties of the Heusler nanoparticles is investigated. The formation of the L2₁ Co₂FeGa phase is confirmed by anomalous X-ray diffraction (AXRD), extended X-ray absorption fine structure (EXAFS), Mössbauer spectroscopy, and magnetic measurements. The degrees of long and short range order of Co₂FeGa nanoparticles decrease for smaller particles. The population of superparamagnetic particles increases with decreasing particle size. The correlation of the TEM-derived particle size and Mössbauer spectroscopy specifies the critical size of Co₂FeGa nanoparticles bridging superparamagnetism and ferromagnetism. It is found that stoichiometric Co₂FeGa phases can be obtained under nonstoichiometric conditions. Pure Co₂FeGa phases are formed at precursor compositions of low Co/Fe ratio, nominal Co and excess Fe. A microscopic study reveals that the size of Co₂FeGa nanoparticles is dependent on the size and morphology of silica supports.

The authors gratefully acknowledge financial support by the DFG (Research Unit FOR 1464 “ASPIMATT”).