Incoherent magnetization reversal in nanowires

The hysteresis of very thin Fe, Co, and Ni nanowires is investigated by model calculations. The considered wires are electrodeposited into self-assembled porous anodic alumina and characterized by wire diameters down to less than 10 nm. The diameter of the wires is smaller than the coherence diameter and therefore favors coherent rotation as compared to curling, but due to imperfections the reversal mode is localized. The localization length is calculated as a function of the wire inhomogenity, and it is shown that the localization reduces both the coercivity and the thermal activation volume (Barkhausen volume). The present calculation provides a semiquantitative explanation of the wires' experimental behavior. (C) 2002 Elsevier Science B.V. All rights reserved.