Green function theory versus Quantum Monte Carlo calculations for thin magnetic films
arXiv:0704.1552 · doi:10.1103/PhysRevB.75.214401
Abstract
In this work we compare numerically exact Quantum Monte Carlo (QMC) calculations and Green function theory (GFT) calculations of thin ferromagnetic films including second order anisotropies. Thereby we concentrate on easy plane systems, i.e. systems for which the anisotropy favors a magnetization parallel to the film plane. We discuss these systems in perpendicular external field, i.e. B parallel to the film normal. GFT results are in good agreement with QMC for high enough fields and temperatures. Below a critical field or a critical temperature no collinear stable magnetization exists in GFT. On the other hand QMC gives finite magnetization even below those critical values. This indicates that there occurs a transition from non-collinear to collinear configurations with increasing field or temperature. For slightly tilted external fields a rotation of magnetization from out-of-plane to in-plane orientation is found with decreasing temperature.
7 pages, 9 figures, accepted for publication in PRB
References in corpus (14)
- Quantum Monte Carlo with Directed Loops
- Stochastic series expansion method with operator-loop update
- Generalized Directed Loop Method for Quantum Monte Carlo Simulations
- Many-body Green's function theory of Heisenberg films
- The ALPS project: open source software for strongly correlated systems
- Monte-Carlo study of the reorientation transition in Heisenberg models with dipole interactions
- Theory of field induced spin reorientation transition in thin Heisenberg films
- Quantum Monte Carlo simulation of thin magnetic films
- Reorientation transition of ultrathin ferromagnetic films
- Anisotropy effects on the magnetic excitations of a ferromagnetic monolayer below and above the Curie temperature
- Ferromagnetism and Temperature-Driven Reorientation Transition in Thin Itinerant-Electron Films
- Phase transition in ultrathin magnetic films with long-range interactions: Monte Carlo simulation of the anisotropic Heisenberg model
- Absence of a Magnetic Phase Transition in Heisenberg, Hubbard, and Kondo-lattice (s-f) Films
- A new type of temperature driven reorientation transition in magnetic thin films