@article{oai:repo.qst.go.jp:00080342,
 author = {Maekawa, Masaki and Miyashita, Atsumi and Sakai, Seiji and Kawasuso, Atsuo and Maekawa, Masaki and Miyashita, Atsumi and Sakai, Seiji and Kawasuso, Atsuo},
 issue = {5},
 journal = {PHYSICAL REVIEW B},
 month = {Aug},
 note = {In this study, Gd ion implantation and annealing were performed at 900 ◦C for nominally undoped wurtzite GaN grown by metal-organic chemical vapor deposition. Spin-polarized positron annihilation measurements showed that vacancy clusters including at least 12 vacancies per cluster were the major positron-trapping centers and that the electrons in the vacancy clusters were spin-polarized. These observations could be explained by first-principles calculations. The previous speculation about the defect-assisted ferromagnetism of Gd-implanted GaN may be supported if vacancy clusters are considered.},
 title = {Gadolinium-implanted GaN studied by spin-polarized positron annihilation spectroscopy},
 volume = {102},
 year = {2020}
}