Systematic Two-band Model Calculations of the GMR Effect with Metallic and Nonmetallic Spacers and with Impurities

TL;DR

This paper uses Green's function calculations to analyze GMR effects in ferromagnetic films with metallic and non-metallic spacers, revealing significant GMR effects especially with non-metallic spacers in ballistic conditions.

Contribution

It provides a systematic computational approach to GMR in layered systems, highlighting the impact of spacer type and impurities on GMR magnitude.

Findings

Large GMR effects predicted for non-metallic spacers in ballistic regime

Impurity effects strongly depend on model parameters

Calculations offer order-of-magnitude estimates for GMR

Abstract

By an accurate Green's function method we calculate conductances and the corresponding Giant Magneto-Resistance effects (GMR) of two metallic ferromagnetic films separated by different spacers, metallic and non-metallic ones, in a simplified model on a sc lattice, in CPP and CIP geometries (i.e. current perpendicular or parallel to the planes), without impurities, or with interface- or bulk impurities. The electronic structure of the systems is approximated by two hybridized orbitals per atom, to mimic s-bands and d-bands and their hybridization. We show that such calculations usually give rough estimates only, but of the correct order of magnitude; in particular, the predictions on the impurity effects depend strongly on the model parameters. One of our main results is the prediction of huge CPP-GMR effects for {\it non-metallic} spacers in the ballistic limit.