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We analyze the depinning transition of a driven interface in the three-dimensional (3D) random field Ising model (RFIM) with quenched disorder by means of Monte Carlo simulations. The interface initially built into the system is perpendicular to the  direction of a simple cubic lattice. We introduce an algorithm which is capable of simulating such an… (More)
We consider the three-dimensional Ising model in a L(⊥)×L(∥)×L(∥) cuboid geometry with a finite aspect ratio ρ=L(⊥)/L(∥) and periodic boundary conditions along all directions. For this model the finite-size scaling functions of the excess free energy and thermodynamic Casimir force are evaluated numerically by means of Monte Carlo simulations. The Monte… (More)
A conserved lattice gas with random neighbor hopping of active particles is introduced which exhibits a continuous phase transition from an active state to an absorbing non-active state. Since the randomness of the particle hopping breaks long range spatial correlations our model mimics the mean-field scaling behavior of the recently introduced new… (More)
The universal finite-size scaling function of the critical Casimir force for the three dimensional XY universality class with Dirichlet boundary conditions is determined using Monte Carlo simulations. The results are in excellent agreement with recent experiments on 4He Films at the superfluid transition and with available theoretical predictions.
Structure and magnetism of iron clusters with up to 641 atoms have been investigated by means of density functional theory calculations including full geometric optimizations. Body-centered cubic (bcc) isomers are found to be lowest in energy when the clusters contain more than about 100 atoms. In addition, another stable conformation has been identified… (More)
The Ni-Mn-Ga shape memory alloy displays the largest shape change of all known magnetic Heusler alloys with a strain of the order of 10% in an external magnetic field of less than one Tesla. In addition, the alloys exhibit a sequence of intermediate martensites with the modulated structures usually appearing at c/a < 1 while the low-temperature… (More)
We investigate a two-dimensional Ising model with long-range interactions that emerge from a generalization of the magnetic dipolar interaction in spin systems with in-plane spin orientation. This interaction is, in general, anisotropic whereby in the present work we focus on the isotropic case for which the model is found to be at its upper critical… (More)
A new contribution to friction is predicted to occur in systems with magnetic correlations: Tangential relative motion of two Ising spin systems pumps energy into the magnetic degrees of freedom. This leads to a friction force proportional to the area of contact. The velocity and temperature dependence of this force are investigated. Magnetic friction is… (More)
Co doped ZnO (Zn(1-x)Co(x)O) is studied as a prototype material for transition metal doped II-VI diluted magnetic semiconductors (DMSs) from first-principles and Monte Carlo simulations. The exchange interactions are calculated using the Korringa-Kohn-Rostoker (KKR) Green's function method. The exchange coupling constants thus obtained are treated in the… (More)
We simulated the classical two-dimensional anisotropic Heisenberg model with full long range di-pole interaction with an algorithm especially designed for long range models. The results show strong evidence for a rst order reorientation transition at a temperature TR < TC for appropriate parameters of the model Hamiltonian.