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Ferromagnetism in multi-band Hubbard models

Tanaka, Akinori; Idogaki, Toshihiro - In: Physica A: Statistical Mechanics and its Applications 297 (2001) 3, pp. 441-484

A constructive approach is presented to study the ferromagnetism in multi-band Hubbard models whose Hamiltonians … in generating the ferromagnetism. We also introduce another type of multi-band Hubbard model which has two orbital states … two electrons on the same state, and show that the ground states of the model also exhibit the ferromagnetism. We stress …

Persistent link: https://www.econbiz.de/10010871645

An efficient multigrid preconditioner for Maxwell’s equations in micromagnetism

Baňas, Ľubomír - In: Mathematics and Computers in Simulation (MATCOM) 80 (2010) 8, pp. 1657-1663

We consider a system of Maxwell’s and Landau-Lifshitz-Gilbert equations describing magnetization dynamics in micromagnetism. The problem is discretized by a convergent, unconditionally stable finite element method. A multigrid preconditioned Uzawa type method for the solution of the algebraic...

Persistent link: https://www.econbiz.de/10011050530

Critical behavior and phase diagrams of a spin-1 Blume–Capel model with random crystal field interactions: An effective field theory analysis

Yüksel, Yusuf; Akıncı, Ümit; Polat, Hamza - In: Physica A: Statistical Mechanics and its Applications 391 (2012) 9, pp. 2819-2832

A spin-1 Blume–Capel model with dilute and random crystal fields is examined for honeycomb and square lattices by introducing an effective-field approximation that takes into account the correlations between different spins that emerge when expanding the identities. For dilute crystal fields,...

Persistent link: https://www.econbiz.de/10011058384

Effects of the bond dilution on the phase diagrams of a spin-1 transverse Ising model with crystal field interaction on a honeycomb lattice

Akıncı, Ümit; Yüksel, Yusuf; Polat, Hamza - In: Physica A: Statistical Mechanics and its Applications 390 (2011) 4, pp. 541-552

A bond diluted spin-1 Ising model with crystal and transverse field interactions is examined for honeycomb lattice by introducing an effective field approximation that takes into account the correlations between different spins that emerge when expanding the identities. The effects of the...

Persistent link: https://www.econbiz.de/10011062414

The ferromagnetic Ising model on a Voronoi–Delaunay lattice

Lima, F.W.S; Moreira, J.E; Andrade, J.S; Costa, U.M.S - In: Physica A: Statistical Mechanics and its Applications 283 (2000) 1, pp. 100-106

We investigate the two-dimensional ferromagnetic Ising model in the Voronoi–Delaunay tesselation. In this study, we assume that the coupling factor J varies with the distance r between the first neighbors as J(r)∝e−αr, with α⩾0. The disordered system is simulated applying the...

Persistent link: https://www.econbiz.de/10011062778

Random field effects on the phase diagrams of spin-1/2 Ising model on a honeycomb lattice

Yüksel, Yusuf; Akıncı, Ümit; Polat, Hamza - In: Physica A: Statistical Mechanics and its Applications 391 (2012) 3, pp. 415-422

The Ising model with quenched random magnetic fields is examined for single Gaussian, bimodal and double Gaussian random field distributions by introducing an effective field approximation that takes into account the correlations between different spins that emerge when expanding the identities....

Persistent link: https://www.econbiz.de/10011063955

Transverse susceptibilities of ferromagnetic spin wave interacting with phonon reservoir, II: Temperature dependence of line shapes

Saeki, Mizuhiko - In: Physica A: Statistical Mechanics and its Applications 390 (2011) 11, pp. 1884-1903

A form of the transverse magnetic susceptibility of a ferromagnetic spin system with a uniaxial anisotropy energy and an anisotropic exchange interaction, interacting with a phonon reservoir, is derived in the spin-wave approximation using the TCLE method, where the phonon reservoir interacts...

Persistent link: https://www.econbiz.de/10010591336