Tailoring Interlayer Exchange Coupling of Ferromagnetic Films Across MgO with Fe Nanoclusters

TL;DR

This study explores how embedding Fe nanoclusters in MgO spacers affects interlayer exchange coupling in Fe and Co magnetic films, revealing tunable magnetic interactions and a significant nano-scaling effect.

Contribution

It demonstrates that Fe nanoclusters can significantly modify and control interlayer exchange coupling, with effects dependent on nanocluster position and material composition.

Findings

Coupling strength varies with nanocluster position and can switch between antiferromagnetic and ferromagnetic.

Fe nanoclusters couple more strongly to Co than to Fe films, by 160%.

Nano-scaling effects enhance coupling differences beyond thin film systems.

Abstract

We investigate the interlayer exchange coupling in Fe/MgO/Fe and Fe/MgO/Co systems with magnetic Fe nanoclusters embedded in the MgO spacer. Samples are grown by molecular beam epitaxy (MBE) and utilize wedged MgO films to independently vary the film thickness and the position of the Fe nanoclusters. Depending on the position of the Fe nanoclusters, the bilinear coupling (J1) exhibits strong variations in magnitude and can even switch between antiferromagnetic and ferromagnetic. This effect is explained by the magnetic coupling between the ferromagnetic films and the magnetic nanoclusters. Interestingly, the coupling of Fe nanoclusters to a Co film is 160% stronger than their coupling to a Fe film (at MgO spacing of 0.56 nm). This is much greater than the coupling difference of 20% observed in the analogous thin film systems (i.e. Fe/MgO/Co vs. Fe/MgO/Fe), identifying an interesting nano-scaling effect related to the coupling between films and nanoclusters.