Growth of skyrmionic MnSi nanowires on Si: Critical importance of the SiO2 layer

MnSi in the B20 structure is a prototypical helimagnet that forms a skyrmion lattice, a vortex-like spin texture under applied magnetic field. We have systematically explored the synthesis of single crystal MnSi nanowires via controlled oxide-assisted chemical vapor deposition and observed a characteristic signature of skyrmion magnetic ordering in the MnSi nanowires. The thickness of the SiO2 layer on the Si substrate plays the key role in obtaining a high yield of B20 MnSi skyrmion nanowires. A growth mechanism was proposed that is consistent with the existence of an optimum SiO2 thickness. A growth phase diagram was constructed based on the extensive studies of various growth conditions for various MnSi nanostructures. The persistence of both the helicoidal and skyrmion magnetic ordering in the one-dimensional wires was directly revealed by ac and dc magnetic measurements.