Introducing and manipulating magnetic dopant exchange interactions in semiconductor nanowires

The ability to control both spin and charge degrees of freedom in semiconductor nanostructrures is at heart of spintronic and quantum information technologies. Magnetically-doped semiconductor nanowires have emerged as a promising platform for spintronics, which warrants the exploration of their synthesis, electronic structure, and magnetic properties. Here we demonstrate the preparation of manganese-doped GaN and SnO2 nanowires by chemical vapor deposition and solvothermal methods, respectively. The investigation of both systems by electron microscopy and x-ray absorption spectroscopy at ensemble and single nanowire levels indicates that manganese dopants exist in a dual oxidation state, Mn²⁺ and Mn³⁺, with Mn²⁺ being the majority species. X-ray magnetic circular dichroism studies of individual nanowires suggest ferromagnetic interactions of manganese dopants, and the nanowire orientation-dependent magnetization owing to the magnetocrystalline anisotropy. The results of these studies demonstrate quantitative determination of the dopant electronic structure at the molecular level, and allow for a prediction of the magnetic properties of diluted magnetic semiconductor nanowires based on their orientation and geometry.