Establishment of spin-polarized positron annihilation and its application to nobel spin phenomena

2014 Fiscal Year Final Research Report

• Project/Area Number: 24310072
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Partial Multi-year Fund
• Section: 一般
• Research Field: Quantum beam science
• Research Institution: Japan Atomic Energy Agency
• Principal Investigator: KAWASUSO Atsuo 独立行政法人日本原子力研究開発機構, 原子力科学研究部門 先端基礎研究センター, 研究員 (20354946)
• Co-Investigator(Kenkyū-buntansha): MAEKAWA Masaki 独立行政法人日本原子力研究開発機構, 原子力科学研究部門 先端基礎研究センター, 研究員 (10354945) ; FUKAYA Yuki 独立行政法人日本原子力研究開発機構, 原子力科学研究部門先端基礎研究センター, 研究員 (40370465)
• Co-Investigator(Renkei-kenkyūsha): SAKAI Seiji 独立行政法人日本原子力研究開発機構, 原子力科学研究部門 先端基礎研究センター, 研究主幹 (10354929) ; SAITOH Eiji 東北大学, 金属材料研究所, 教授 (80338251)
• Project Period (FY): 2012-04-01 – 2015-03-31
• Keywords: スピン / 陽電子 / スピントロニクス / 磁性 / 表面 / ハーフメタル / 原子空孔 / ポジトロニウム

Outline of Final Research Achievements

We found that the electron momentum distributions of 3d and 4f ferromagnets show that (i) asymmetry upon magnetic field reversal, (ii) the asymmetry is proportional to their magnetizations, (iii) the asymmetry vanishes above the Curie temperatures. Furthermore, we found that the differential spectrum of electron momentum distribution　between majority and minority spin bands of Fe is well reproduced by the first principles band calculation. From the spin-polarized electron momentum distributions of full and half Heusler alloys (Co2MnSi(Al) and NiMnSb), we found higher half-metallicity of Co2MnSi and NiMnSb. Through spin-polarized positronium annihilation measurement, we found the appearance of surface spin polarizations on nonmagnetic Pd, Pt, Ta, W and Bi/Ag bilayer due to application of DC current. From spin polarized positron annihilation measurements for ZnO and SnO2, we found that cation vacancies have magnetic momemt.

Free Research Field

物性物理、陽電子