Interface characterization of Co2MnGe/Rh2CuSn Heusler multilayers

TL;DR

This study investigates the interface quality and diffusion effects in Co2MnGe/Rh2CuSn Heusler multilayers, revealing early diffusion at moderate temperatures and a magnetically dead layer impacting magnetoresistance.

Contribution

It provides detailed analysis of diffusion and interface disorder in all-Heusler multilayers using advanced spectroscopy techniques, highlighting factors affecting device performance.

Findings

Diffusion begins at 200-250°C, especially for Mn.

Presence of a 4 Å magnetically dead layer.

Interface diffusion correlates with low magnetoresistance.

Abstract

All-Heusler multilayer structures have been investigated by means of high kinetic x-ray photoelectron spectroscopy and x-ray magnetic circular dichroism, aiming to address the amount of disorder and interface diffusion induced by annealing of the multilayer structure. The studied multilayers consist of ferromagnetic Co$_2$MnGe and non-magnetic Rh$_2$CuSn layers with varying thicknesses. We find that diffusion begins already at comparably low temperatures between 200 $^{\circ}$C and 250 $^{\circ}$C, where Mn appears to be most prone to diffusion. We also find evidence for a 4 {\AA} thick magnetically dead layer that, together with the identified interlayer diffusion, are likely reasons for the small magnetoresistance found for current-perpendicular-to-plane giant magneto-resistance devices based on this all-Heusler system.