Superconducting Transport Properties of NiFe Artificial Spin Ice and Nb Hybrid Structure

Abstract

We report the influence of magnetic NiFe artificial spin ice (ASI) on the transport properties of superconducting Nb thin film. Resistivity (ρ) as a function of temperature (T ~ 1.8 to 300 K) and magnetic field (B ~ 0 to 40 kOe in parallel and perpendicular orientations with respect to the film plane) has been examined for two samples, a plain Nb thin film and a hybrid thin film of NiFe-ASI and Nb (Nb-NiFe). The impact of the magnetic NiFe-ASI on superconducting Nb is clearly visible in the transport properties, where, in comparison with plain Nb, for the Nb-NiFe hybrid thin film: (1) the normal state resistivity increases by a factor ~ 1.5; (2) the superconducting transition temperature (Tc) at B = 0 reduces from 7.31 to 6.51 K; (3) the surface sheath superconductivity vanishes as reflected by the parallel upper critical field, Bc2(T); and (4) the perpendicular Bc2(T) is suppressed in the entire T range. Interestingly, with the applied field, $$ {T}_{\mathrm{c}}^{\mathrm{Nb}}-{T}_{\mathrm{c}}^{\mathrm{Nb}-\mathrm{NiFe}} $$ |B increases in perpendicular and decreases in parallel field orientation. The magnetoresistance measurements near Tc for our Nb-NiFe hybrid thin film show shallow minima revealing matching pinning effects with respect to the ASI square lattice. The results are understood in terms of the thin film nature of our samples, geometrically frustrated magnetism of ASI and the proximity between the magnetic NiFe-ASI and superconducting Nb at the interface.