  Free-standing ferromagnetic nano-membranes with thicknesses below 10 nm could
effectively be used for spin selective filtering of electrons. Such membranes
can work both as spin detectors in electron-spectroscopy, -microscopy and
-diffraction as well as a source of spin polarized electrons. Theoretical
studies and previous work has indicated that ferromagnetic membranes of a few
nm have Sherman functions in the 30-60 % range and would provide an effective
alternative to current spin detection technology. Here we demonstrate the
fabrication of gold capped Co nano-membranes with a 2.6 nm Co layer and a total
thickness below 10 nm. The membranes have a Sherman function $S\approx 0.41$
and a transmission of $3.7\times 10^{-2}$ for electron energies of 2 eV. The
integration of such spin-filtering membranes in a hemispherical electron
analyzer is shown to provide massively parallel detection capabilities and a
"2-dimensional" figure of merit $FOM_\mathrm{2D}$ = 67.2, the highest reported
to date.
