@misc{oai:repo.qst.go.jp:00072707,
 author = {前川, 雅樹 and 境, 誠司 and 和田, 健 and 宮下, 敦巳 and 河裾, 厚男 and 前川 雅樹 and 境 誠司 and 和田 健 and 宮下 敦巳 and 河裾 厚男},
 month = {Oct},
 note = {Some semiconductor materials of metal oxides or nitrides, such as zinc oxide (ZnO) or gallium nitride (GaN), exhibit d0 ferromagnetism, which may be induced by lattice defects. From theoretical calculations, cation vacancies are the most probable sources of d0 ferromagnetism. However, conventional measurement techniques hardly demonstrate directly that cation vacancies act as ferromagnetic centers. Spin-polarized positron annihilation spectroscopy (SP-PAS) is a unique technique, which can detect magnetic moments associated with vacancies. From the magnetic Doppler-broadening (MDB) spectrum, magnetic moments at vacancies can be detected. In this study, we attempted to detect vacancy-induced magnetism in ZnO and GaN by the SP-PAS method.
 To create vacancies, oxygen and nitrogen ions were implanted to the undoped ZnO and p-type GaN crystal, respectively. The range of ion implantation was estimated to be 100 nm from the surface. The magnetization curves obtained at 30 K using SQUID measurement show the induced ferromagnetism upon implantation. The MDB spectra were measured in the magnetic field of ±0.91 T at 30K.  For unimplanted state, the intensity of MDB spectra are nearly null, suggesting the lack of magnetic moments at vacancies. By implantation, finite MDB intensities appear in both samples. Also, the MDB spectrum shapes were theoretically reproduced assuming cation vacancies. These confirm the existence of magnetic moments at cation vacancies and those are the source of the ferromagnetism observed by SQUID., ISSS-8国際会議参加・発表のため},
 title = {Vacancy-induced magnetism in metal oxides or nitrides probed by spin-polarized positron beam},
 year = {2017}
}