Crossover between ballistic and diffusive regime of the spin-conductance and CPP-GMR in magnetic multilayered nanostructures

TL;DR

This paper investigates how disorder and band structure influence spin-conductance and GMR in magnetic multilayers, analyzing ballistic, diffusive, and localized regimes and their crossover using advanced numerical simulations.

Contribution

It introduces a comprehensive analysis of disorder effects on CPP-GMR, including multiple disorder models, and explores the crossover between transport regimes with large-scale simulations.

Findings

Disorder reduces mean free path, affecting GMR magnitude.

Different disorder types lead to distinct GMR behaviors.

Crossover regimes exhibit complex interplay between ballistic and diffusive transport.

Abstract

We analyze the interplay between disorder and band structure in current perpendicular to the planes (CPP) giant magnetoresistance (GMR). We consider finite magnetic multilayers attached to pure crystalline leads, described by a tight-binding simple cubic two-band model (s-d). Several models of disorder are considered, including random on-site potentials, lattice distortions, impurities, vacancies, and cross-section fluctuations. Magneto-transport properties are calculated in the zero-temperature zero-bias limit, within the Landauer-Buttiker formalism. Using a very efficient numerical scattering technique, we are able to perform simulations, over large length scales, and to investigate spin-transport in the ballistic, diffusive and localized regimes, as well as the crossover between them. The competition between disorder-induced mean free path reduction and disorder-induced spin asymmetry enhancement of the conductance highlights several different regimes of GMR.