Vortex lattice symmetry break in nanostructured Nb thin films
An advanced mask-less nanofabrication technique, focused electron beam-induced deposition (FEBID), has been employed on epitaxial Nb thin films for their ferromagnetic decoration by an array of Co stripes. These substantially modify the non-patterned films' superconducting properties, providing a washboard-like pinning potential landscape for the vortex motion. At small magnetic fields B<0.1T, vortex lattice matching effects have been investigated by magneto-transport measurements. Peculiarities in the field dependencies of the films resistivity R(B) have been observed in particular for the vortex motion perpendicular to the Co stripes. The deduced field values correspond to the vortex lattice parameter matching the pinning structure's period, whereas no fields matching the stripe width have been observed, as it was reported previously [D. Jaque et al., Appl. Phys. Lett. 81, 2851 (2002)] for Nb films grown on periodically distributed submicrometric lines of Ni.