The low energy electron reflectivity from a magnetic surface depends on the
relative orientation between the electron spin and the sample magnetizatio
n. This effect has been exploited for realizing a new electron spin polariz
ation detector. As a scattering surface we have used a well ordered Fe(001)
-p(1x1)O surface, which is stable against surface contamination and gives r
ise to very large spin dependent effects. We describe in detail the prepara
tion in vacuum of such a target surface and show that it can be transferred
in a separate system, without performance losses. The analyzing power S of
the detector is given by the relative variation of its response when the t
arget magnetization is reversed. We find extremely large S values for elect
rons reflected at 3-6 eV kinetic energy, with maximum above 45%, i.e., roug
hly 3 times better than other polarimeters presently used. (C) 1999 America
n Institute of Physics. [S0034-6748(99)02109-7].