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MA: Magnetismus
MA 29: Magnetische Materialien
MA 29.2: Vortrag
Dienstag, 8. März 2005, 15:30–15:45, TU A060
The minority gap in half-metallic ferromagnets — •Hem C. Kandpal, Gerhard H. Fecher, Claudia Felser, and Gerd Schönhense — Johannes Gutenberg - Universität, 55099 Mainz, Germany
Half-metallic ferromagnets like the full Heusler compounds with formula X2YZ are supposed to show an integer value for the total magnetic moment. SCF calculations reveal, however, in certain cases of X = Co based compounds, non-integer values in contrast to experiments. Co2YSi with Y = Mn, Fe are of particular interest because of there high TC. In order to explain deviations of the magnetic moment calculated for such compounds, the dependency of the minority gap on the lattice parameter was studied by using FLAPW calculations. The minimum total energy (relaxed structure) of Co2FeSi is found for the experimental lattice parameter. But, the relaxed structure does not show half metallic ferromagnetic behavior. However, if we increase the relaxed lattice constant by +8%, it shows half-metallic ferromagnetism and a magnetic moment equal to 6µB in accordance to the experimental value. While Co2MnSi is a half metallic ferromagnet for the experimental lattice constant, the size of the minority gap still depends on the lattice parameter used in the calculations. Recently there is an increased interest in thin films of the Heusler compounds. In this situation, the lattice parameter may be changed if the thin films consist of strained layers. Therefore, one may observe experimentally different results with respect to the width of the gap and magnetic moments compared to bulk samples.
(This work is funded by the DFG in FG 559.)