Monte Carlo Simulations for Models of Dipolarly Interacting Fine Magnetic Particles

摘要

Systems of dipolarly coupled classical spins with uniaxial anisotropy and isotropic distribution of anisotropy axes are used as schematic models of interacting fine magnetic particles. The spins are placed in crystalline arrays with varying numbers of nearest neighbours N, i.e. in tetragonal lattices with N=2 and 4, diamond lattice, simple cubic, fcc and bcc lattices. Periodic boundary conditions are assumed, and Ewald summation is used for the dipolar interactions. A choice of results from extensive Monte Carlo simulations are reported with respect to various aspects of the magnetic properties of these models, specifically hysteresis at zero temperature, temperature dependent magnetization, non-equilibrium simulations of the response in alternating fields. These results establish dependences of magnetic properties for these models on the underlying spatial arrangement of the particles. The results are discussed in relation to simple mean-field theories for the magnetic properties of ensembles of magnetic fine particles.