Münster 1997 – wissenschaftliches Programm

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AM: Magnetismus

AM 6: Magnetische Phasenübergänge in drei- und niederdimensionalen Strukturen

AM 6.7: Vortrag

Montag, 17. März 1997, 18:45–19:00, F4

Magnetic Phases of correlated electrons in nondegenerate and degenerate band — •Marcus Fleck¹, Andrzej M. Oleś^1,2, and Lars Hedin¹ — ¹Max-Planck-Institut für Festkörperforschung, Heisenbergstrasse 1, D-70569 Stuttgart, Germany — ²Institut of Physics, Jagellonian University, Reymonta 4, PL-30059 Kraków, Poland

We investigate the magnetic instabilities of the nondegenerate (s band) and degenerate (d band) Hubbard models in two dimensions using the electron interactions renormalized by particle-particle diagrams. The Stoner parameter is strongly reduced in the s band case and ferromagnetism survives only close to the Van Hove singularity and for a flat band in the Γ - X(Y) directions. In contrast, the renormalizations are much weaker in the d band case and the magnetic states are stabilized by Hund’s rule spin correlations.