Angular dependence of switching properties in single Fe nanopillars

Abstract

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 0 degrees to 90 degrees to the applied sinusoidal field. The field period is 15 ns, and the particle size is 9 × 9 × 150 nm. The system is discretized into a rectangular pillar of 7 × 7 × 101 spins each with uniform magnetization. At low angles, reversal begins at the endcaps and proceeds toward the center of the particle. At ninety degrees, 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 1 × 1 × 17 spins, does not agree with experiment, but shows behavior very similar to that of the Stoner-Wohlfarth model of coherent rotation.

Magnetization reversal behavior in complex shaped Co nanowires: A nanomagnet morphology optimization

“…as expected from the Stoner-Wohlfarth model). The effect of the morphology (cylinder compared to the prolate ellipsoid) is given by the lower values of both fields which was confirmed also in previous works [30]. This drop is, of coarse, more visible when the magnetic field is applied along the nanowires (ϕ H = 0 o ) than when they are close to the perpendicular direction (ϕ H = 90 o ).…”

Magnetization reversal in elongated Fe nanoparticles

“…Recent micromagnetic simulation of defect-free d=9 nm Fe nanopillars by Brown et al 26,27 showed that nucleation can start at both ends and propagate through the whole pillars in the time scale of nanoseconds. The calculated H sw is about 2 kOe for the fields applied parallel to the easy axis, which is close to our experimental value.…”

Finite-Temperature Simulations for Magnetic Nanostructures

“…In this section we summarize recent simulation results for magnetization reversal in iron nanopillars 40 , and further evaluate these results in light of additional experimental data on such reversal. Figure 2a shows hysteresis loops at T = 100 K for the full micromagnetic model with the field misaligned at 0 • , 45 • , and 90 • to the long axis of the particle.…”

“…In this section we summarize recent simulation results for magnetization reversal in iron nanopillars 40 , and further evaluate these results in light of additional experimental data on such reversal.…”