Scanning SQUID Imaging of Epitaxial Semiconductor-Magnetic Insulator Heterostructures*

Semiconductor nanowires with epitaxially grown superconductor are a promising potential host for Majorana bound states. The addition of a magnetic insulator to the system has been shown to induce Zeeman splitting in the nanowire via proximity effect, eliminating the need for an external magnetic field to produce a topologically nontrivial state. We use scanning SQUID microscopy (SSM) to study 2D heterostructures of thin film EuS, a magnetic insulator, on InAs and InSb substrates. Our measurements are a local probe of magnetism as a function of temperature, allowing us to characterize the homogeneity and domain structure of possible proximity-induced magnetism in this magnetic insulator/semiconductor structure. We report the local Curie temperature as a function of the EuS layer thickness and substrate material. These results contribute to a more thorough understanding of the magnetic coupling between EuS and InAs/InSb, which can inform design choices for future devices.