Resistance of multilayers with long length scale interfacial roughness

TL;DR

This paper investigates how large-scale interfacial roughness affects the electrical resistance of magnetic multilayers, revealing that it can either increase or decrease resistance depending on electron mean free paths and geometry.

Contribution

It provides a theoretical analysis of resistance changes in multilayers with long-scale roughness using the Boltzmann equation, applicable to magnetic multilayer systems.

Findings

Resistance decreases in CPP when mean free paths are short.

Resistance increases in both CPP and CIP when mean free paths are long.

Interface roughness can either enhance or reduce giant magnetoresistance.

Abstract

The resistance of multilayers with interface roughness on a length scale which is large compared to the atomic spacing is computed in several cases via the Boltzmann equation. This type of roughness is common in magnetic multilayers. When the electronic mean free paths are small compared to the layer thicknesses, the current flow is non-uniform, and the resistance decreases in the Current-Perpendicular-to-Plane (CPP) configuration and increases in the Current-In-Plane (CIP) configuration. For mean free paths much longer than the layer thicknesses, the current flow is uniform, and the resistance increases in both the CPP and CIP configurations due to enhanced surface scattering. In both the CPP and CIP geometries, the giant magnetoresistance can be either enhanced or reduced by the presence of long length scale interface roughness depending on the parameters. Finally, the changes in the CPP and CIP resistivities due to increasing interface roughness are estimated using experimentally determined parameters.