Vectorial multichannel-spin-polarimetry and the analysis of spin-transport in metal-organic interfaces
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Abstract
Photoemission spectroscopy has become the key technique for the investigation of electronic
properties of promising materials such as Heusler compounds, Weyl systems, materials
exhibiting a strong Rashba effect, topological insulators or hybrid metal-organic
interfaces. During the last decade photoemission spectroscopy without spin resolution
enjoyed a considerable increase in performance due to parallel image detection while the
spin polarization analysis of a given electron beam remained time consuming. Since potential
candidates for spintronic applications such as metal-organic interfaces tend to degrade
within a short period, a massive reduction of spin-resolved data acquisition time is crucial.
A newly developed high-performance imaging spin filter system based on a large Ir(001)
scattering crystal tackles this issue by enhancing the measurement efficiency. An increase
of the effective figure of merit by a factor of over 103 in contrast to standard single-channel
detectors is presented together with a detailed characterization of the experimental setup.
Furthermore, the spectrometer resolution, spin filter preparation and lifetime are reviewed.
An energy and angular resolution of 27 meV and 0.23◦ has been determined for an energy
and angular acceptance of 1.5 eV and ±10◦. The spin filter efficiency is analyzed by
mapping a broad range of scattering energy and azimuthal angle. A Sherman function
of up to 0.44 has been measured under ideal conditions. If the scattering plane coincides
with a mirror plane of the crystal, the spin filter is only sensitive to the component of
the spin vector perpendicular to the scattering plane. A scattering plane that does not
coincide with a crystal mirror plane yields a high sensitivity to spin vector components
that are parallel to the scattering plane. A spin rotator element enables the independent
determination of the two in-plane components of the spin vector. By combining three or
six scattering conditions a vectorial spin analysis becomes possible for both, magnetic and
non-magnetic samples.
Spin-resolved spectra of Fe/W(110) and H2TPP films of different thickness on Fe/W(110)
are measured with the efficient multichannel spin-resolving photoemission spectrometer
and with the ESPRESSO spectrometer at the Hiroshima Synchrotron Radiation Center.
The experimental results allow for a determination of the spin diffusion length within the
molecular film.