AN IMPROVED ALGORITHM FOR MICROMAGNETICS

We present an improved micromagnetic model for predicting the minimum energy magnetization states in fine magnetite grains. The resolution, or the number of elemental magnetization vectors, has been increased o ver previous models: first, by the use of a Fourier transform algorith m to reduce the number of calculations from O(N-2) to O(N log N) (N be ing the number of elements into which the grain is subdivided); and se cond, by implementing the model on a parallel computer. Using a parall el computer reduces the computation time by a factor of approximately 1/(4N(p)), where N-p represents the number of processors. The improved model enables equilibrium magnetization states to be predicted using a resolution of 64 x 64 x 64 subcubes to a grain in 16 hours of CPU ti me; this compares with a resolution of 12 x 12 x 12 in 24 hours of CPU time for previous models. High-resolution models allow the examinatio n of multidomain states in materials such as magnetite and different s ized grains or assemblages of interacting grains.