An efficient three-dimensional demagnetizing field calculation method.

摘要

Computer simulations of three dimensional micromagnetic dynamics are useful for understanding magnetic materials and in the design of recording devices. The most computationally intensive part of such simulations is the calculation of long-range magnetostatic (or “demagnetizing”) interactions. The ability to compute these interactions faster, for larger systems, is essential for realistic modelling of magnetic materials. We present an efficient demagnetizing field calculation method. This method combines a one dimensional fast Fourier transform (FFT) method and a variant of Greengard's two dimensional fast multipole method. We explore adaptive techniques which adjust the order of the multipole expansion in response to the local magnetization state. Adaptive techniques allow us to focus more computational power on critical domain wall regions than on the bulk volume. We present the sequential and parallel versions of our method. Also we compare the accuracy and performance of the method with other methods, and incorporate it into a production three dimensional simulation code. This new method parallelizes well and uses less memory than the three dimensional FFT method. The computational complexity of the adaptive fast multipole method scales linearly with problem size as compared with alternate methods.