Comparison of magnetostatic field calculation methods on two-dimensional square grids as applied to a micromagnetic standard problem

Magnetization reversal modes and coercivities were calculated for a magneti c particle with thickness : width : length aspect ratios 0.1 : 1 : 5 as a f unction of the reduced particle width d/l(ex), where d is the particle widt h and l(ex) is the intrinsic magnetostatic exchange length. With only excha nge energy and magnetostatic energy included, the particle corresponds to m MAG standard problem No. 2. The problem is modeled with two-dimensional gri ds of three-dimensional spins, and the results are compared for two methods of calculating magnetostatic energies, the "constant magnetization'' metho d and the "constant charge'' method. For both magnetostatic computational m ethods, the coercivity decreases from H-c/M-s = 0.06+/-0.003 to 0.014+/-0.0 03 over the range 3 < d/l(ex)<80, where the uncertainties reflect the field step size. Also over this interval, as d/l(ex) increases, the magnetizatio n exhibits three modes of reversal: nearly uniform rotation, transverse swi tching of end domains followed by propagation of head-to-head domain walls from the ends to the center of the particle, and nucleation and propagation of vortices accompanied by more complex domain structures. (C) 1999 Americ an Institute of Physics. [S0021-8979(99)65708-5].