Magnetic Skyrmion Phase in MnSi Thin Films

Abstract

Detailed magnetometry and polarized neutron reflectometry studies were conducted on MnSi thin films grown epitaxially on Si(111) substrates. It is demonstrated that with an in-plane applied field H || [110], a broadly stable skyrmion phase exists at elevated temperatures and fields. Magnetometry and transport measurements with an out-of-plane applied field H || [111] prove that no skyrmion phase exists in this geometry. However, Hall effect measurements in this geometry show unexpected evidence of a topological Hall effect. This can be explained with a multi-dimensionally modulated cone phase, which proves that contrary to recent literature, a topological Hall effect is not sufficient proof of skyrmions. The results of this thesis represent a significant step towards a technologically relevant material in which skyrmions are broadly stable. A material of this type could be used in novel magnetic storage devices and signi ficantly impact our future computing capabilities.