Biomedical subjects

T Kontos

Publications and source records attributed to T Kontos.

3 recordsLinked to original sources

PubMed2003

Phase sensitive experiments in ferromagnetic-based Josephson junctions.

We have measured the ground state of ferromagnetic Josephson junctions using a single dc SQUID (superconducting quantum interference device).We show that the Josephson coupling is either positive (0 coupling) or negative (pi coupling) depending on the ferromagnetic layer thickness. As expected, the sign change of the Josephson coupling is observed as a shift of half a quantum flux in the SQUID diffraction pattern when operating in the linear limit.

Journal Article↗

PubMed2002

Josephson junction through a thin ferromagnetic layer: negative coupling.

We investigate Josephson coupling through a ferromagnetic thin film using superconductor-insulator-ferromagnet-superconductor planar junctions. Damped oscillations of the critical current are observed as a function of the ferromagnetic layer thickness. We show that they result from the exchange energy gained or lost by a quasiparticle Andreev-reflected at the ferromagnet-superconductor interface. The critical current cancels out at the transition from positive ("0") to negative ("pi") coupling, in agreement with theoretical calculations.

Journal Article↗

PubMed2001

Inhomogeneous superconductivity induced in a ferromagnet by proximity effect.

Planar tunneling spectroscopy reveals damped oscillations of the superconducting order parameter induced into a ferromagnetic thin film by the proximity effect. The oscillations are due to the finite momentum transfer provided for Cooper pairs by the splitting of the spin-up and spin-down bands in the ferromagnet. As a consequence, for negative values of the superconducting order parameter the tunneling spectra are capsized ("pi state"). The oscillations' damping and period are set by the same length scale, which depends on the spin polarization.

Journal Article↗