Spin polarized tunneling in MgO-based tunnel junctions with superconducting electrodes

TL;DR

This paper investigates spin-polarized electron tunneling in MgO-based magnetic tunnel junctions with superconducting electrodes, analyzing polarization, scattering, and symmetry filtering effects to understand giant magnetoresistance.

Contribution

It introduces a detailed study of spin polarization and symmetry filtering in MgO-based junctions with superconducting electrodes, comparing different ferromagnetic materials.

Findings

Polarization varies with electrode material and annealing temperature.

Symmetry filtering enhances tunneling magnetoresistance ratios.

Spin-orbit scattering and pair-breaking parameters are quantified.

Abstract

We prepared magnetic tunnel junctions with one ferromagnetic and one superconducting Al-Si electrode. Pure cobalt electrodes were compared with a Co-Fe-B alloy and the Heusler compound Co2FeAl. The polarization of the tunneling electrons was determined using the Maki-Fulde-model and is discussed along with the spin-orbit scattering and the total pair-breaking parameters. The junctions were post-annealed at different temperatures to investigate the symmetry filtering mechanism responsible for the giant tunneling magnetoresistance ratios in Co-Fe-B/ MgO/ Co-Fe-B junctions.