  Nanowires can serve as flexible substrates for hybrid epitaxial growth on
selected facets, allowing for design of heterostructures with complex material
combinations and geometries. In this work we report on hybrid epitaxy of
semiconductor - ferromagnetic insulator - superconductor (InAs/EuS/Al) nanowire
heterostructures. We study the crystal growth and complex epitaxial matching of
wurtzite InAs / rock-salt EuS interfaces as well as rock-salt EuS /
face-centered cubic Al interfaces. Because of the magnetic anisotropy
originating from the nanowire shape, the magnetic structure of the EuS phase
are easily tuned into single magnetic domains. This effect efficiently ejects
the stray field lines along the nanowires. With tunnel spectroscopy
measurements of the density of states, we show the material has a hard induced
superconducting gap, and magnetic hysteretic evolution which indicates that the
magnetic exchange fields are not negligible. These hybrid nanowires fulfil key
material requirements for serving as a platform for spin-based quantum
applications, such as scalable topological quantum computing.
