Spin and energy analysis of electron beams: Coupling a polarimeter based on exchange scattering to a hemispherical analyzer

Abstract

We have coupled a high efficiency polarimeter based on exchange scattering from a magnetized target to a hemispherical analyzer. The target is a Fe(001)-p(1×1)O surface which gives rise to highly spin-dependent scattering in the 4–6 eV electron kinetic energy range. Due to the low scattering energy, the design of the transfer electron optics from the analyzer exit slit to the target is really crucial. We describe in detail the adopted solution along with the performances of the entire apparatus. For low values of the analyzer pass energy we have measured an overall efficiency of 7×10−4 with an analyzing power (Sherman function) of 0.2. As an example of application spin-resolved photoemission data from Fe(001) are reported.

Comment on “High efficiency electron spin polarization analyzer based on exchange scattering at Fe/W(001)” [Rev. Sci. Instrum. 79, 083303 (2008)]

“…As one may expect, these results are similar to those obtained with other spin polarimeters based on the same principle. 3,4,10 Nevertheless, at this state of the experimental setup only qualitative and not quantitative comparisons with other detectors can be made, since a rigorous characterization would involve the measurement of the spin polarization of the incident electron beam as well as the characterization of the Fe film and the oxygen structure deposited on W͑001͒. We obtain 27% and 54% spin polarization for the secondary electrons from the 12 ML Fe/Cu͑001͒ and the photoelectrons from 6 ML Co/Cu͑001͒, respectively.…”

“…Certainly, the addition of oxygen as method to increase the operative time of the detector has been previously reported. 3,4 In the measurements shown in Fig. 1, the Fe film has not been dosed with O 2 .…”

“…1 does not involve a significant enhancement in the stability. In fact, whereas Bertacco et al 3,4 characterize the oxygen coverage on the Fe film ͑30 L of O 2 at 450 K and then flash heated for a few seconds͒ by means of low-energy electron diffraction measurements to obtain a perfect p͑1 ϫ 1͒ structure, in Ref. 1 this structure is only expected to form following a different procedure ͑3-5 L and then annealing at 600 K͒.…”

“…Note that this does not have any effect when measuring asymmetry but influences the result of the calculation of the figure of merit. Therefore, with this experimental setup only qualitative comparisons with other spin detectors 3,4 and spin detection techniques 8,9 can be made.…”

“…In Fig Furthermore, at this state of the experimental setup, one has to assume values for P from other experiments to derive the figure of merit and therefore a rigorous comparison with other detectors 3,4 in which polarization-calibrated electron sources were used, 5-7 cannot be made. Also the uncertainty of I / I 0 in the calculation of the figure of merit makes difficult a quantitative comparison with other detectors.…”