Asymmetric critical current of niobium microbridges with ferromagnetic stripe

Abstract

A highly asymmetric current-voltage (IV) characteristic is reported in long Nb microbridges with a ferromagnetic cobalt overlayer. In the hysteretic regime, asymmetry as high as 100% was observed between forward and reverse critical currents. Such an asymmetry is a result of the competing magnetic fields produced at the edge of the bridge due to the bias current and the magnetic overlayer. While the temperature dependence of the critical current in the shallow branch of hysteretic IV curves (Ic−) followed a typical Ginzburg–Landau (GL) behavior, Ic+, the critical current of the other branch increased more sharply at low temperature. Local heating of the bridge due to the bias current was found to have no significant effect on the nature of critical current asymmetry.

Non-reciprocity of vortex-limited critical current in conventional superconducting micro-bridges

“…2 (a)]. Diode effect in SC/ferromagnet hybrids has been reported previously, where the ferromagnet is metallic [38][39][40] and insulating 41 . We chose to study an SC/MI hybrid owing to its advantages for non-dissipative electronics, and to eliminate a parallel electron transport channel.…”

Preferentially directed flux motion in a very thin superconducting strip with nanostructured profile

“…This results, for a certain range of magnetic field applied perpendicular to the substrate, in an uncommon voltage-current [V(I)] curve a) of the strip, characterized by vanishingly small asymmetry in the positive and negative critical currents but appreciably large asymmetry in the voltages. We remark that asymmetric V(I) curves with considerable asymmetry in the critical currents rather than in the voltages have been reported [38][39][40][41][42][43] in ferromagnet-superconductor hybrids on the micron scale and, very recently, in single thin superconducting strips having plano-convex cross section when subjected to a homogeneous magnetic field applied parallel to the substrate. 44 Both the peculiar behavior of the V(I) curve of the strip reported in the present case and the more general problem of the geometrical force experienced by the vortices are addressed here in the framework of time dependent Ginzburg-Landau model for superconductors.…”

Ubiquitous Superconducting Diode Effect in Superconductor Thin Films

“…The diode effect in SC/FM bilayers has been reported in other systems including LSMO/YBCO 23 , Nb/Co 13,24 and Py/Nb 25,26 heterostructures. The phenomenon could be understood by a screening current mechanism 13 shown schematically in Fig.…”