Direct surface charging and alkali-metal doping for tuning the interlayer magnetic order in planar nanostructures

TL;DR

This paper demonstrates that surface charge modification and alkali-metal doping can effectively control interlayer magnetic order and magnetic anisotropy in nanostructures, enabling magnetic state tuning at small scales.

Contribution

It introduces surface charge alteration techniques and alkali-metal adsorption as novel methods for tuning magnetic interactions and anisotropy in planar nanostructures.

Findings

Modest surface charge can switch magnetic alignment between ferromagnetic and antiferromagnetic.

Alkali metal adsorption reverses interlayer magnetic order.

Alkali overlayers significantly enhance perpendicular magnetic anisotropy in FePt films.

Abstract

The continuous reduction of magnetic units to ultra small length scales inspires efforts to look for a suitable means of controlling magnetic states. In this study we show two surface charge alteration techniques for tuning the interlayer exchange coupling (IEC) of ferromagnetic layers separated by paramagnetic spacers. Our study reveals that already a modest amount of extra charge can switch the mutual alignment of the magnetization from anti-ferromagnetic to ferromagnetic or vice verse. We also propose adsorption of alkali metals as an alternative way of varying the electronic and chemical properties of magnetic surfaces. Clear evidence is found that the interlayer magnetic order can be reversed by adsorbing alkali metals on the magnetic layer. Moreover, alkali metal overlayers strongly enhance the perpendicular magnetic anisotropy in FePt thin films. These findings combined with atomistic spin model calculations suggest that electronic or ionic way of surface charging can have a crucial role for magnetic hardening and spin state control.