First-principles studies of modulated Co/Cu superlattices with strongly and weakly exchange-biased Co-monolayers leading to a ferrimagnetic ground state

TL;DR

This study uses first-principles calculations to analyze exchange interactions in modulated Co/Cu superlattices, revealing a ferrimagnetic ground state due to competing exchange biases in Co monolayers.

Contribution

It provides a detailed first-principles analysis of exchange integrals in modulated CoCu superlattices, identifying conditions leading to a ferrimagnetic ground state.

Findings

Exchange integrals have opposite signs for 3 ≤ n ≤ 6.

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

The ground state is ferrimagnetic for the studied n-values.

Abstract

First-principles calculations have been performed in order to determine effective exchange integrals between strongly and weakly exchange-biased Co monolayers in the modulated CoCu$_2$/CoCu$_n$ superlattices. For $3\le n\le 6$ it has been found that the respective exchange integrals have opposite signs and differ for $n\ne 4$ from each other by one order of magnitude and for $n=4$ still by a factor of $\sim 1.7$. The obtained phase diagram, with all the relevant magnetic phases, shows that for the $n$-values considered, the ground state configuration is ferrimagnetic.