MAGNETIC AFTEREFFECT IN QUASI-1D AMORPHOUS FERROMAGNETIC NANOCOLUMNS

2.5 nm wide amorphous ferromagnetic nanocolumns were prepared by swift heavy ions irradiation of paramagnetic YCo2 thin films. The shape ani sotropy-induced coercive field He is approximately half the anisotropy field HA. Magnetic aftereffect measurements reveal that the activatio n volume involved during magnetization reversal is comparable to the p article size, Given the small diameters involved, such a behaviour can be addressed either by Stoner-Wohlfarth rotation with surface perturb ation or to the end-surface nucleation of a 1-D domain wall. For the l ater, an upper bound of the coercive field, estimated by considering a simple planar configuration, yields a reduced H-c/H-A ratio in agreem ent with the experimental value.