Angular dependence of switching properties in single Fe nanopillars

The continued increase in areal densities in magnetic recording makes it crucial to understand magnetization reversal in nanoparticles. We present finite-temperature micromagnetic simulations of hysteresis in Fe nanopillars with the long axis tilted at angles from 0degrees to 90degrees to the applied sinusoidal field. The field period is 15 ns, and the particle size is 9x9x150 nm. The system is discretized into a rectangular pillar of 7x7x101 spins each with uniform magnetization. At low angles, reversal begins at the endcaps and proceeds toward the center of the particle. At 90degrees reversal proceeds along the entire length of the particle (save at the ends). The switching field was observed to increase over the entire range of angles, consistent with recent experimental observations. A second, lower-resolution micromagnetic simulation with 1x1x17 spins, does not agree with experiment, but shows behavior very similar to that of the Stoner-Wohlfarth model of coherent rotation. (C) 2004 American Institute of Physics.