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Microscopic conditions favoring itinerant ferromagnetism: Hund's rule coupling and orbital degeneracy

Abstract

The importance of Hund's rule coupling for the stabilization of itinerant ferromagnetism is investigated within a two-band Hubbard model. The magnetic phase diagram is calculated by finite-temperature quantum Monte Carlo simulations within the dynamical mean-field theory. Ferromagnetism is found in a broad range of electron fillings whereas antiferromagnetism exists only near half filling. The possibility of orbital ordering at quarter filling is also analyzed.Comment: 5 pages, 6 figures, RevTeX, final version contains an additional phase diagram for smaller Hund's rule coupling. to appear in Eur. Phys. J. B (1998

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