Helical surface magnetization in nanowires: the role of chirality

Nanomagnetism is nowadays expanding into three dimensions, triggered by the discovery of new magnetic phenomena and their potential use in applications. This shift towards 3D structures should be accompanied by strategies and methodologies to map the tridimensional spin textures associated. We present here a combination of dichroic X-ray transmission microscopy at different angles and micromagnetic simulations allowing to determine the magnetic configuration of cylindrical nanowires. We have applied it to permalloy nanowires with equispaced chemical barriers that can act as pinning sites for domain walls. The magnetization at the core is longitudinal and generates at the surface of the wire helical magnetization. Different types of domain walls are found at the pinning sites, which respond differently to applied fields depending on the relative chirality of the adjacent domains.