Spontaneous supercurrent induced by ferromagnetic pi junctions.

0-pi Josephson tunnel junctions with ferromagnetic barrier.

We fabricated high quality Nb/Al2O3/Ni(0.6)Cu(0.4)/Nb superconductor-insulator-ferromagnet-superconductor Josephson tunnel junctions. Using a ferromagnetic layer with a steplike thickness, we obtain a 0-pi junction, with equal lengths and critical currents of 0 and pi parts. The ground state of our 330 microm (1.3lambda(J)) long junction corresponds to a spontaneous vortex of supercurrent pinne...

Observation of spin-triplet superconductivity in Co-based Josephson junctions.

We have measured a long-range supercurrent in Josephson junctions containing Co (a strong ferromagnetic material) when we insert thin layers of either PdNi or CuNi weakly ferromagnetic alloys between the Co and the two superconducting Nb electrodes. The critical current in such junctions hardly decays for Co thicknesses in the range of 12-28 nm, whereas it decays very steeply in similar junctio...

Half-integer Shapiro steps at the 0-pi crossover of a ferromagnetic Josephson junction.

We investigate the current-phase relation of S/F/S junctions near the crossover between the 0 and the pi ground states. We use Nb/CuNi/Nb junctions where this crossover is driven both by thickness and temperature. For a certain thickness a nonzero minimum of critical current is observed at the crossover temperature. We analyze this residual supercurrent by applying a high frequency excitation a...

Triplet superconductivity in a ferromagnetic vortex.

We argue that triplet superconductivity can be conveniently realized in hybrid superconductor-ferromagnet (S-F) structures with a ferromagnetic vortex. We demonstrate that due to proximity-induced long-range triplet pairing such S-F-S junctions can sustain appreciable supercurrent which can be directly measured in experiments. Depending on the contact geometry either zero- or π-junction regime ...

Spontaneous Magnetic Flux Induced by Ferromagnetic π-Junctions