Observation of a high negative spin polarization at the Fe/MgO(100) surface oxidized at room temperature

Abstract

Spin polarization of an Fe/MgO(100) surface oxidized at room temperature has been analyzed with a spin-polarized metastable helium beam, which is an extremely surface sensitive spin probe, under high magnetic fields (0–50 kOe). The spin polarization of the Fe surface, although it initially decays with oxygen exposure, increases at >20 L (1 L=10−6 Torr sec) and becomes comparable to that observed for a clean Fe surface at >100 L. The polarization is negative and especially high at around the Fermi level. This may be understood if we assume the formation of Fe3O4.

Surface Spin Polarization of Fe Nanoclusters

“…A positive asymmetry indicates that minority electrons dominate in the surface vacuum region of the clusters, agreeing with SPMDS studies of thin Fe films [8]- [10]. High positive asymmetries have been reported before for thin Fe films on various substrates including GaAs (15 %) [8], MgO(100) (9 %) [9], Ag(100) (6 %) [9], and W(110) (24 %) [7].…”

Magnetic properties of O2adsorbed on Cu(100): A spin-polarized metastable He beam study

“…5) and Cu(100) (Ref. 7) clarified the exchange splittings in the oxygen 1s excitation spectra, while no such splitting was observed for the chemisorbed state. Niki et al, based on the observation that the presence of physisorbed O 2 molecules largely affects the ortho-para conversion rate of H 2 , suggested that physisorbed O 2 on Ag is magnetic.…”

“…The spin state is important especially when characterizing a physisorbed O 2 molecule, which is bonded weakly to the surface via the van der Waals interaction and therefore is gas-phase like. Physisorbed O 2 has been identified on various metallic surfaces such as Ag, [1][2][3][4] Pt, 5,6 Cu, 7,8 and Ni, 9 and its spin state has been discussed in a number of studies. [3][4][5]7 Near-edge x-ray absorption fine structure (NEXAFS) measurements of O 2 physisorbed on Pt(111) (Ref.…”

“…[3][4][5]7 Near-edge x-ray absorption fine structure (NEXAFS) measurements of O 2 physisorbed on Pt(111) (Ref. 5) and Cu(100) (Ref. 7) clarified the exchange splittings in the oxygen 1s excitation spectra, while no such splitting was observed for the chemisorbed state.…”

“…Niki et al, based on the observation that the presence of physisorbed O 2 molecules largely affects the ortho-para conversion rate of H 2 , suggested that physisorbed O 2 on Ag is magnetic. 4 No electron spin resonance signal, however, has been detected for physisorbed O 2 on Ag, but this absence has been ascribed to the broadening of the resonance due to the coupling with substrate conduction electrons. 3 Following these studies, physisorbed O 2 is likely to be magnetic, but there has been no experiment that directly detected the spin polarization of O 2 adsorbed on metallic substrates.…”