Ryutaro Kodaira

Synthesis and structural characterization of vertical ferromagnetic MnAs/semiconducting InAs heterojunction nanowires

The purpose of this study is to synthesize vertical ferromagnetic/semiconducting heterojunction nanowires by combing the catalyst-free selective-area growth of InAs nanowires and the endotaxial nanoclustering of MnAs and to structurally and magnetically characterize them. MnAs penetrates the InAs nanowires to form nanoclusters. The surface migration length of manganese adatoms on the nanowires, which is estimated to be 600 nm at 580 °C, is a key to the successful fabrication of vertical MnAs/InAs heterojunction nanowires with atomically abrupt heterointerfaces.

Shape control of ferromagnetic MnAs nanoclusters exhibiting magnetization switching in vertical MnAs/InAs heterojunction nanowires

We report in detail on the growth time dependence of ferromagnetic MnAs nanoclusters in vertical MnAs/InAs heterojunction nanowires and the analysis of magnetization switching in a heterojunction nanowire. The size of MnAs nanoclusters increases with increasing growth time of MnAs nanoclusters. In addition, we observe the magnetization and magnetization switching in one of the MnAs nanoclusters with a relatively large height parallel to the c-axis, i.e., the magnetic hard axis, possibly owing to the magnetic shape anisotropy along the c-axis, after the application of external magnetic fields nearly parallel to the c-axis of MnAs nanoclusters. These results suggest that the growth time of MnAs nanoclusters is a key to controlling the size, shape, and even magnetization of MnAs nanoclusters in vertical MnAs/InAs heterojunction nanowires.