Spin- and angle-resolved inverse photoemission setup with spin orientation independent from electron incidence angle

A new spin- and angle-resolved inverse photoemission setup with a low-energy (5-100 eV) electron source is presented. The spin-polarized electron source, with a compact design, can decouple the spin polarization vector from the electron beam propagation vector, allowing to explore any spin orientation at any wavevector in angle-resolved inverse photoemission. The beam polarization can be tuned to any preferred direction with a shielded electron-optical system, preserving the parallel beam condition. We demonstrate the performances of the setup by measurements on Cu(001), Au(111) and ultrathin Co films. We estimate at room temperature the energy resolution of the overall system to be $\sim170$ meV from $kT_{eff}$ of a Cu(001) Fermi level, allowing a direct comparison to photoemission. The spin-resolved operation of the setup has been demonstrated by measuring the Rashba splitting of the Au(111) Shockley surface state. The effective polarization of the electron beam is $P=30\pm3$% and the wavevector resolution is $\Delta k_{F}\lesssim0.06$A$^{-1}$. Measurements on ultrathin Co films with out-of-plane magnetization and on Au(111) surface state demonstrate how the electron beam polarization direction can be tuned in the three spatial dimensions. In both systems the maximum of the spin asymmetry is reached when the electron beam polarization is aligned with the out-of-plane magnetization of the Co film or the in-plane spin-polarization of Au(111) surface state.