Two modes of magnetization switching in a simulated iron nanopillar in an obliquely oriented field

Finite-temperature micromagnetics simulations are employed to study the magnetization-switching dynamics driven by a field applied at an angle to the long axis of an iron nanopillar. A bimodal distribution in the switching times is observed, and evidence for two competing modes of magnetization-switching dynamics is presented. For the conditions studied here, temperature T = 20.2 K and the reversal field 3260 Oe at an angle of 75° to the long axis, approximately 60% of the switches involve unstable decay (no free-energy barrier) and 40% involve metastable decay (a free-energy barrier is crossed). The latter are indistinguishable from switches that are constrained to start at a metastable free-energy minimum. Competition between unstable and metastable decay may not be confined to the temperature studied in this paper, and could greatly complicate applications involving magnetization switching near the coercive field.