Spin polarized current and Andreev transmission in planar superconducting/ferromagnetic Nb/Ni junctions

TL;DR

This study investigates spin-polarized tunneling and Andreev reflection in Nb/Ni superconducting/ferromagnetic junctions, revealing insights into current polarization and barrier structure through experimental measurements and theoretical modeling.

Contribution

It introduces a simple theoretical model to analyze spin polarization and barrier properties in Nb/Ni junctions without magnetic fields, across various temperatures.

Findings

Measured current polarization without magnetic field.

Fitted experimental data with a consistent theoretical model.

Gained microscopic insight into oxide barrier structure.

Abstract

We have measured the tunnelling current in Nb/Nb$_x$O$_y$/Ni planar tunnel junctions at different temperatures. The junctions are in the intermediate transparency regime. We have extracted the current polarization of the metal/ferromagnet junction without applying a magnetic field. We have used a simple theoretical model, that provides consistent fitting parameters for the whole range of temperatures analyzed. We have also been able to gain insight into the microscopic structure of the oxide barriers of our junctions.%