Construction of a Spin-Polarized Positronium Time-of-Flight Measurement Apparatus

M. Maekawa, K. Wada, A. Miyashita, A. Kawasuso Quantum Beam Science Research Directorate, National Institutes for Quantum and Radiological Science and Technology, 1233 Watanuki, Takasaki, Gunma, 370-1292, Japan

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For the measurement of the energy-resolved spin polarization of the outermost surface of materials, a spin-polarized positronium time-of-flight spectrometer has been developed. For the non-magnetic material (Pt film) and ferromagnetic material (Ni film), spin-polarized positronium time-of-flight measurements were carried out. Although no significant intensity appears for the Pt sample, a clear negative intensity is observed around the Ps work function energy for the Ni sample. This means that the spin polarization of the outermost electron is negative near the Fermi energy. The spin-polarized positronium time-of-flight method would be a unique tool in the measurement of spin-polarized band structure of outermost electrons due to its energy resolvability and surface selectivity.

DOI:10.12693/APhysPolA.137.105 topics: spin-polarized positron beam, positronium time-of-flight, electron spin polarization, Fermi level