Interlayer Exchange Coupling Beyond the Proximity Force Approximation

TL;DR

This paper presents a new theoretical approach to understanding interlayer exchange coupling in trilayer systems, especially when interface roughness and phase coherence effects are significant, extending beyond the proximity force approximation.

Contribution

It introduces a phase coherence-based model that captures interference effects in interlayer exchange coupling, revealing new features when interface roughness is comparable to the Fermi momentum.

Findings

Enhanced exchange coupling due to interface roughness explained.

New resonant transmission channels identified.

Model reproduces proximity force approximation for mild corrugations.

Abstract

Ion bombardment has been shown to be capable of enhancing the interlayer exchange coupling in a trilayer system that exhibits giant magnetoresistance. We demonstrate that this phenomenon can be derived from the phase coherence among scattered paths within the two rough interfaces when their topographies are correlated. In the case of mild corrugations, our method reproduces the predictions by the proximity force approximation which does not consider the interference. When the characteristic Fourier conjugate of the tomography becomes large and comparable to the Fermi momentum, interesting new features arise and can only be captured by our more general approach. Among our findings, the scenario of an enhanced interlayer exchange coupling due to the interface roughness is explained, along with how it depends on the sample parameters. An additional channel for the resonant transmission is identified due to extra scattering paths from the roughness.