Oak Ridge Collaboration: Fast Micromagnetic Simulation

Pieter Visscher and Dmytro Apalkov, Physics and Astronomy

Oak Ridge National Laboratory is developing a suite of public-domain materials-simulation programs (ψ-Mag), including one for micromagnetic simulation of magnetic materials and devices. We have visited ORNL to develop and integrate a new version of the Fast Multipole Method (FMM) for the calculation of magnetostatic interactions. Our
new version uses Cartesian harmonics rather than the spherical harmonics [Ylm(θ,φ)] conventionally used. The efficiency of the two methods have been compared for the first time by the Oak Ridge group, in a new report [“Flexible Fast Multipole Method for Magnetic Simulations”, by Gregory Brown, Thomas C. Schulthess, D. M. Apalkov, and
P. B. Visscher, IEEE Transactions on Magnetics, v. 40, issue 4, 2004]. The surprising result is that the UA Cartesian method is about 7 times faster than the conventional spherical harmonic method. This is a significant result, since
the time-consuming nature of magnetostatic (“demagnetization”) field calculation is currently one of the most important barriers to the widespread use of such modeling in magnetism research.