The effect of surface oxidation and crystal thickness on magnetic properties and magnetic domain structures of Cr2Ge2Te6

TL;DR

This study explores how surface oxidation and crystal thickness influence the magnetic properties and domain structures of Cr2Ge2Te6, revealing that oxidation modifies magnetic behavior and domain sizes, which is crucial for device design.

Contribution

It provides a systematic analysis of oxidation and thickness effects on magnetic domains and properties in Cr2Ge2Te6, highlighting how controlled oxidation can manipulate magnetic features.

Findings

Oxidation forms a ~5 nm oxide layer after 5 days in ambient conditions.

Oxidation increases the Cr ion oxidation state, altering magnetic properties.

Thickness affects stripe domain width and skyrmionic bubble size in pristine crystals.

Abstract

Van der Waals (vdW) magnetic materials such as Cr2Ge2Te6 (CGT) show promise for novel memory and logic applications. This is due to their broadly tunable magnetic properties and the presence of topological magnetic features such as skyrmionic bubbles. A systematic study of thickness and oxidation effects on magnetic domain structures is important for designing devices and vdW heterostructures for practical applications. Here, we investigate thickness effects on magnetic properties, magnetic domains, and bubbles in oxidation-controlled CGT crystals. We find that CGT exposed to ambient conditions for 5 days forms an oxide layer approximately 5 nm thick. This oxidation leads to a significant increase in the oxidation state of the Cr ions, indicating a change in local magnetic properties. This is supported by real space magnetic texture imaging through Lorentz transmission electron microscopy. By comparing the thickness dependent saturation field of oxidized and pristine crystals, we find that oxidation leads to a non-magnetic surface layer which is thicker than the oxide layer alone. We also find that the stripe domain width and skyrmionic bubble size are strongly affected by the crystal thickness in pristine crystals. These findings underscore the impact of thickness and surface oxidation on the properties of CGT such as saturation field and domain/skyrmionic bubble size and suggest a pathway for manipulating magnetic properties through a controlled oxidation process.