Magnetic sublayers effect on the exchange coupling oscillations vs. cap-layer thickness

TL;DR

This study investigates how the magnetic sublayers influence the oscillatory behavior of interlayer exchange coupling as a function of cap-layer thickness, revealing conditions for suppression and the global nature of IEC oscillations.

Contribution

It introduces a new selection rule involving magnetic sublayers affecting IEC oscillations and analyzes the distribution of induced magnetic moments across sublayers.

Findings

IEC oscillations can be suppressed if extremal vectors do not match.

Magnetic moments distribution reveals material-specific periodicity.

IEC oscillations depend on all sublayers, not just spacer and cap layers.

Abstract

We have found that some periods of interlayer exchange coupling (IEC) oscillations as a function of cap-layer (CL) thickness may be suppressed if the in-plane extremal spanning vectors of the cap- and ferromagnet-materials Fermi surfaces do not coincide. The suppression of the IEC oscillations vs. the CL thickness holds also if the magnetic slab thickness tends to infinity. On the one hand, we have shown by means of very simple arguments that apart from the well-known selection rules concerning the spacer- and cap-layers, another one related with the magnetic sublayers has to be fulfilled in order that the interlayer coupling oscillations $vs.$ CL thickness could survive. On the other hand, the distribution of induced magnetic moments across the non-magnetic cap- and spacer-sublayers have been computed and shown to reveal the underlying periodicity of the materials they are made of (i.e. related to their bulk Fermi surfaces) independently of whether or not the selection rules are fulfilled. This means that the IEC oscillations are of global nature and depend on all the sublayers the system consists of.