Anisotropic magnetoresistive response in thin Nb films decorated by an array of Co stripes

The magnetoresistive response of as-grown and nano-structured thin Nb films was studied by transport measurements performed in a rotating-current scheme at different temperatures. Epitaxial Nb(110) oriented thin films have been prepared by DC magnetron sputtering onto a-plane (11 (2) over bar0) sapphire substrates. Periodically arranged unidirected Co stripes have been deposited onto the substrates using focused electron beam induced deposition (FEBID) which represents a direct nanofabrication tool with a lateral resolution down to several tens of nanometres. A pronounced eight-shaped form of polar diagrams of the magnetoresistivity rho(T, alpha) and the critical current density j(c)(T, alpha) has been observed for the nano-structured films with alpha denoting the current direction with respect to the Co stripes. This eight-shaped form of rho(T, alpha) and j(c)(T, alpha) proves that a washboard pinning potential is invoked in the films by the unidirected Co stripes. The FEBID process is demonstrated to provide a new pathway towards mask-less nano-patterning by ferromagnetic decoration of a superconducting film, which is promising with regard to controlling its resistive response in the mixed-state.