First principles studies of modulated Co/Cu superlattices with strongly and weakly exchange biased Co-monolayers

TL;DR

This study uses first-principles calculations to analyze exchange interactions in modulated Co/Cu superlattices, revealing opposite signs for strong and weak couplings and implications for spin valve applications.

Contribution

It provides the first detailed computational analysis of exchange integrals in modulated Co/Cu superlattices with non-equivalent Co planes, highlighting their complex dependence and potential for spintronic devices.

Findings

Strong coupling is antiferromagnetic for n=3 to 6.

Weak coupling is ferromagnetic for n=3 to 6.

Exchange integrals differ by an order of magnitude for n≠4.

Abstract

First-principles calculations have been performed in order to determine effective exchange integrals between {\it strongly} and {\it weakly} exchange-coupled Co monolayers in certain modulated periodic $CoCu_2/CoCu_n$-type superlattices with three non-equivalent Co planes, which have not yet been studied hitherto. For $3\le n\le 6$ we find that the two non-equivalent exchange integrals have opposite signs, i.e.~the strong coupling is antiferromagnetic and the weak coupling ferromagnetic, and differ for $n\ne 4$ from each other by one order of magnitude. It is shown that the results depend on the system as a whole and could not be obtained from separate parts. Finally we suggest that ''spin valve'' systems of such kind should be considered when trying to obtain good magneto-resistance together with low switching-fields.