Magnetic fluctuations and itinerant ferromagnetism in two-dimensional systems with Van Hove singularities

Journal Article · Thu Nov 15 00:00:00 EST 2007 · Journal of Experimental and Theoretical Physics

DOI:https://doi.org/10.1134/S1063776107110167· OSTI ID:21075658

Igoshev, P A

A criterion for ferromagnetism in two-dimensional systems with the Fermi level near Van Hove singularities (VHSs) is analyzed. In the quasistatic approximation applied to a spin-fermion model, it is shown that the spectrum of spin excitations (paramagnons) is positively defined when the interaction I between the electronic and spin degrees of freedom is sufficiently large (I > I{sub c}). The critical interaction I{sub c} is much greater than its value determined from the Stoner criterion; hence, the latter criterion is not an adequate criterion for ferromagnetism in the presence of Van Hove singularities in the electronic spectrum. By combining the quasistatic approximation with the method of equations of motion, the electronic self-energy is obtained in the first order in the inverse number of spin components.

• OSTI ID: 21075658
• Journal Information: Journal of Experimental and Theoretical Physics, Vol. 105, Issue 5; Other Information: DOI: 10.1134/S1063776107110167; Copyright (c) 2007 Nauka/Interperiodica; Article Copyright (c) 2007 Pleiades Publishing, Inc; Country of input: International Atomic Energy Agency (IAEA); ISSN 1063-7761
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
APPROXIMATIONS
DEGREES OF FREEDOM
EQUATIONS OF MOTION
EXCITATION
FERMI LEVEL
FERMIONS
FERROMAGNETISM
FLUCTUATIONS
INTERACTIONS
MAGNONS
SELF-ENERGY
SINGULARITY
SPECTRA
SPIN
TWO-DIMENSIONAL CALCULATIONS