Effect of interface bonding on spin-dependent tunneling from the oxidized Co surface

TL;DR

This paper introduces a factorization approach to analyze spin-dependent tunneling, demonstrating how surface oxidation affects spin filtering and conductance in Co surfaces.

Contribution

It generalizes Julliere's formula using a new factorization method and shows how oxidation modifies spin-dependent tunneling properties.

Findings

Oxygen monolayer creates a spin-filter effect.

Oxidation switches conductance from minority to majority spin dominance.

The factorization approach explains tunneling behavior in oxidized surfaces.

Abstract

We demonstrate that the factorization of the tunneling transmission into the product of two surface transmission functions and a vacuum decay factor allows one to generalize Julliere's formula and explain the meaning of the ``tunneling density of states'' in some limiting cases. Using this factorization we calculate spin-dependent tunneling from clean and oxidized fcc Co surfaces through vacuum into Al using the principal-layer Green's function approach. We demonstrate that a monolayer of oxygen on the Co (111) surface creates a spin-filter effect due to the Co-O bonding which produces an additional tunneling barrier in the minority-spin channel. This changes the minority-spin dominated conductance for the clean Co surface into a majority spin dominated conductance for the oxidized Co surface.