Vectorial spin polarization detection in multichannel spin-resolved photoemission spectroscopy using an Ir(001) imaging spin filter

We report on spin- and angular-resolved photoemission spectroscopy using a high-resolution imaging spin filter based on a large Ir(001) crystal enhancing the effective figure of merit for spin detection by a factor of over ${10}^3$ compared to standard single-channel detectors. Furthermore, we review the spin filter preparation and its lifetime. The spin filter efficiency is mapped on a broad range of scattering energies and azimuthal angles. Large spin filter efficiencies are observed for the spin component perpendicular as well as parallel to the scattering plane depending on the azimuthal orientation of the spin filter crystal. A spin rotator capable of manipulating the spin direction prior to detection complements the measurement of three observables, thus allowing for a derivation of all three components of the spin polarization vector in multichannel spin polarimetry. The experimental results nicely agree with spin-polarized low-energy electron diffraction calculations based on a fully relativistic multiple scattering method in the framework of spin-polarized density functional theory.

Figure 1

Experimental setup showing a cross section of the transfer lens and hemispherical analyzer (red) and spin filter part (blue). The out-of-plane spin component orientation is marked by red and blue arrows. The longitudinal magnetic field for the spin-polarization manipulation is marked by green arrows. Electron lenses schematic.

Figure 2

(a) Detector image of the low-energy cutoff of secondary electrons produced by an electron gun. (b) Corresponding intensity profiles determined at three different emission angles as marked by the white rectangles. (c) Detector image of the angular slit array and (d) line profiles determined at three different scattering energies.

Figure 3

The lifetime of the spin filter is evaluated from a measurement series of three hours under constant conditions.

Figure 4

(a) Scattering plane of the spin filter and spin polarization component notations with respect to the incoming beam and the spin filter surface (red and green). The mirror planes of a fourfold symmetric crystal are marked as yellow dashed lines. The spin filter can be rotated about its surface normal (angle $\phi$). (b) Schematic LEED pattern of the Ir(001)-($5\times 1$) surface. The used axis definition is overlayed.

Figure 5

Intensity, asymmetry and relative FoM maps of $P_n$ (a)–(c) and $P_e$ (d)–(f) polarization components for scattering energies of 5–15 eV and a scattering angle of ${45}^{\circ }$ as a function of the azimuthal angle.

Figure 6

Intensity, asymmetry and relative FoM maps of $P_n$ (a)–(c) and $P_e$ (d)–(f) polarization components for scattering energies of 34-44 eV and a scattering angle of ${45}^{\circ }$ as a function of the azimuthal angle.

Figure 7

(a) Measured asymmetry at $E_{\mathrm{scatt}}=10\mathrm{eV}$ and azimuthal angles between $\pm {45}^{\circ }$ for different spin polarization rotation angles. (b), (c) The image is rotated from $0^{\circ }\text{–}{40}^{\circ }$ (spin from $0^{\circ }\text{–}{80}^{\circ }$) so that the former $P_n$ component transforms nearly into a $P_e$ component.

Figure 8

Theoretically determined spin-orbit induced asymmetry for the $P_e$ (a), (b) and $P_n$ (c), (d) component of the electron polarization in the range of 6–15 eV (a), (c) and 34–44 eV (b), (d).