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MA: Magnetismus

MA 12: Elektronentheorie

MA 12.3: Talk

Saturday, March 5, 2005, 09:30–09:45, TU EMH225

Self-consistent determination of magnon dispersions in the s-d(f) exchange model — •Tilmann Hickel and Wolfgang Nolting — Lehrstuhl Festkörpertheorie, Institut für Physik, Humboldt-Universität zu Berlin, Newtonstr. 15, 12489 Berlin

In many materials the ferromagnetic order is assumed to be due to an indirect interaction of localized magnetic moments via itinerant electrons of a conduction band. This mechanism is described in the s-d(f) exchange model (also called Kondo-lattice or double-exchange model). Many-body theoretical approaches to the model often focus on the self-energy of the itinerant subsystem, while treating the local-moment subsystem less accurate. We have developed an projection-operator approach to the s-d(f) exchange model that avoids this inequality of the subsystems. It combines the state-of-the-art knowledge on the density of states with a temperature-dependent determination of magnon dispersions and softening effects. In our evaluation we will focus on the latter. Compared to earlier predictions, the obtained magnetization curves yield a further reduction of the paramter regime where ferromagnetism can be expected.