Spin filtering effect on secondary electrons crossing an iron overlayer

Spin polarization (SP) measurements of the secondary electron yield from ferromagnetic interfaces is a sensitive probe of surface and interface magnetism. By exploiting the jumps of the total photoionization cross section in correspondence of the L-edge excitation in transition metals one introduces a chemical sensitivity in the SP via the enhancement of the secondary emission from a specific magnetic or non magnetic specie at the interface. The hν-dependence of the SP in overlayer experiments allows to derive accurately the total and spin-dependent attenuation lengths for secondary electrons in non-magnetic and ferromagnetic materials.