Scale ratio modulated magnetic anisotropy of 3D Ni1-xCox crossed nanowire networks

Velázquez Galván, Yenni G. [UCL] da Câmara Santa Clara Gomes, Tristan [UCL] Piraux, Luc [UCL] de la Torre Medina, Joaquín [Instituto de Investigaciones en Materiales – Unidad Morelia, Universidad Nacional Autónoma de México, Morelia, Mexico]

In this work, three dimensional (3D) interconnected Ni1−xCox (0 ⩽ x ⩽ 100%) crossed nanowire (CNW) networks with different scale ratios have been fabricated in order to investigate the influence of size reduction of the whole 3D networks structure on their crystal orientation and magnetic properties. Interconnected porous polycarbonate membranes, each one with different nanopore diameters but with the same porosity, have been designed to obtain porous architectures with different scale ratios. Using these membranes, CNW networks with the same packing fraction of about 22%, but different nanowires (NWs) diameters have been grown by electrodeposition. As a result, the magnetostatic (MS) anisotropy in the saturated state is the same for all the 3D networks, which allows identifying size dependent magnetic anisotropies. Reducing the diameter of the nanowires leads to changes on their magnetic properties, so that Co-rich CNW networks show a magnetocrystalline (MC) anisotropy contribution originated by a preferential hexagonal close packed orientation that competes with the MS anisotropy field. In turn, low diameter Ni-rich CNW networks show an anisotropy contribution of different nature than the MS and MC fields. The strategy presented in this work to accurately separate magnetic contributions leads to a better understanding of the magnetic behavior of complex 3D nanoarchitectures and to their potential use in the development of magnetic, sensing and spintronic applications.