抄録
The saturation spin polarization of secondary electrons from a clean Ni (110) surface was quantitatively measured at 0.094 after careful calibration of a compact Mott detector installed in an Auger electron analyzer for strict inspection of the cleanness of the surface. The spin-dependent mean absorption length of Ni (110) was deduced to be about four layers of Ni (110), that is, λ+= 1.016 nm and λ _= 0.972 nm for the majority spin and minority spin electrons, respectively, from the primary electron energy dependence of the yield and the asymmetry of secondary electrons. The saturation spin polarization was reduced to 0.060, that is, 64% of that for the clean Ni (110) surface, after only 1 hour in a UHV chamber (2×10-7Pa) following a cleaning procedure, for sub-mono-layer oxygen-chemisorbed Ni (110). A model of anti-ferromagnetic Ni spin moments resulting from 180-degree super-exchange through oxygen atoms in the first layer, based on reported STM observations of Ni-O atomic arrangement, is proposed for use in further investigations to explain this drastic reduction in the polarization, which must be very sensitive to the surface magnetic configuration.
