Comment on "High efficiency electron spin polarization analyzer based on exchange scattering at Fe/W(001)" [Rev. Sci....

A recent article [Winkelmann et al., Rev. Sci. Instrum. 79, 083303 (2008)] reports on a compact detector to analyze the electron spin based on exchange scattering at Fe(001) thin film grown on W(001) with chemisorbed oxygen in the p(1x1) structure. The results obtained with the same detector without oxygen coverage show, however, a better performance in terms of both asymmetry and figure of merit. It is also argued that the characterization performed only allows to make qualitative comparisons with other existing detectors based on the same exchange scattering since the polarization of the incident beam has not been measured in situ.