van der Waals Epitaxy of Co_10–xZn_10–yMn_x+y Thin Films: Chemical Composition Engineering and Magnetic Properties

Abstract

Topologically protected magnetic skyrmions have raised interest for future spintronics applications. One of the main challenges is the synthesis of room temperature skyrmion-hosting materials that are compatible with thin-film technology. We present an approach to produce strain-free epitaxial thin films of Co10–x Zn10–y Mn x+y using molecular beam epitaxy. Bulk Co10–x Zn10–y Mn x+y is known to host skyrmions at room temperature for specific composition ratios. Our substrate consists of graphene on oxidized silicon. The van der Waals interactions of the grown material with graphene prevents covalent bonding and corresponding strain. We show how defects in the graphene foster nucleation that results in three different kinds of morphologies: islands, columns, and merged films. Susceptibility measurements suggest a phase transition close to room temperature. We detect up to three spin waves resonances suggesting relatively low magnetic damping. This growth technique opens a new route for the integration of complex alloys and skyrmionic device concepts with silicon electronics.