Magnetization Reversal Mechanism in FeCoNiB Nanowire Arrays

Abstract

The structural and magnetic properties of Fe13Co15.5Ni51.5B20 nanowire arrays have been investigated. The easy axis would be expected to lie along the nanowire axis, due to the contribution of the shape anisotropy. However, the c axis of Co in the alloy results in an orientation perpendicular to the nanowires as it has been observed from the hysteresis loops. Changing the current values results in changes of the deposition potential, allowing a percentage increase or decrease in the deposition of Ni, Co and Fe. This leads to a change of the easy axis from the axial to transverse direction. Coercivity values obtained from the magnetic hysteresis loops allowed the study of the magnetization reversal processes. It has been shown that the reversal process occurs as a result of the nucleation of a single domain with a volume 200 times smaller than the volume of the nanowire. The switching field for the investigated nanowires is explained based on the 'curling' mode given by the model for infinite cylinders. The calculated values of the reduced coercivity h c show that 'curling' alone cannot explain the magnetization reversal. This allowed us to state that it must be a multi-domain structure with domains aligned along the transverse direction. Thus, the magnetization reversal would consist not of a single wall displacement but a series of them.