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Dresden 2011 – scientific programme

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MA: Fachverband Magnetismus

MA 52: Magnetic Thin Films III

MA 52.7: Talk

Thursday, March 17, 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”).

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