CONICET | Buscador de Institutos y Recursos Humanos

Co?Pd nanowires with smallgrain size are fabricated by AC electrodeposition into hexagonally orderedalumina pores,20?35 nm in diameter and about1 mm long. The Effects of the alloycomposition, the nanowire diameter and the grain size on the hysteresis propertiesare considered. X-ray diffraction indicates that the nanowires are single phase,a fcc Co?Pd solid solution; electron microscopy results show that they are polycrystalline,with randomly oriented grains(7?12nm), smaller than the wire diameter. Nanowirearrays are ferromagnetic, with an easy magnetization axis parallel to the nanowirelong axis. Both, the coercive field and the loop squareness monotonously increasewith the Co content and with the grain size, but no clear correlation with the wirediameter is found.The Co and Co-rich nanowire arrays exhibit coercive fieldsand reduced remanence values quite insensitive to temperature in the range 4K? 300Kon the contrary, in Pd-rich nanowires both magnitudes are smaller and they largelyincrease during cooling below 100K. These behaviors are systematized by consideringthe strong dependences displayed by the magneto-crystalline anisotropy and the saturationmagnetostriction on composition and temperature. At low temperatures the effectiveanisotropy value and the domain-wall width to grain size ratio drastically change,promoting less cooperative and harder nucleation modes.