Electronic structure and magnetism of Mn dopants in GaN nanowires: Ensemble vs single nanowire measurements

Abstract

We studied the electronic structure and magnetization of Mn dopants in GaN nanowires at the ensemble and single nanowire levels by near edge x-ray absorption fine structure spectroscopies. The results of single nanowire measurements indicate that Mn adopts tetrahedral coordination in GaN nanowires and has mixed oxidation state (Mn2+/Mn3+), with Mn2+ being in relative majority. Ensemble nanowire spectra suggest co-deposition of Mn secondary phases alongside nanowires. Single nanowire x-ray magnetic circular dichroism indicates intrinsic magnetic ordering of Mn dopants at 300 K. In contrast, as-grown nanowire samples show only residual magnetization, due to nanowire orientation dependence of magnetization.