Document Type
Article
Original Publication Date
2008
Journal/Book/Conference Title
Physical Review B
Volume
77
Issue
20
DOI of Original Publication
10.1103/PhysRevB.77.205411
Date of Submission
April 2015
Abstract
Extensive calculations based on density functional theory have been carried out to understand the origin of magnetism in undoped ZnO thin films as found in recent experiments. The observed magnetism is confirmed to be due to Zn, instead of O, vacancy. The main source of the magnetic moment, however, arises from the unpaired 2p electrons at O sites surrounding the Zn vacancy with each nearest-neighbor O atom carrying a magnetic moment ranging from 0.490to0.740μB. Moreover, the study of vacancy-vacancy interactions indicates that in the ground state, the magnetic moments induced by Zn vacancies prefer to ferromagnetically couple with the antiferromagnetic state lying 44meV higher in energy. Since this is larger than the thermal energy at room temperature, the ferromagnetic state can be stable against thermal fluctuations. Calculations and discussions are also extended to ZnO nanowires that have larger surface to volume ratio. Here, the Zn vacancies are found to lead to the ferromagnetic state too. The present theoretical study not only demonstrates that ZnO samples can be magnetic even without transition-metal doping but also suggests that introducing Zn vacancy is a natural and an effective way to fabricate magnetic ZnO nanostructures. In addition, vacancy mediated magnetic ZnO nanostructures may have certain advantages over transition-metal doped systems in biomedical applications.
Rights
Wang, Q., Sun, Q., Chen, G., et al. Vacancy-induced magnetism in ZnO thin films and nanowires. Physical Review B, 77, 205411 (2008). Copyright © 2008 American Physical Society.
Is Part Of
VCU Physics Publications
Comments
Originally published by the American Physical Society at: http://dx.doi.org/10.1103/PhysRevB.77.205411