NEUTRON REFLECTOMETRY WITH POLARIZATION ANALYSIS - A THEORY AND A NEWSPECTROMETER

We present a complete theory of neutron reflection from a magnetic mul tilayer in the presence of an external magnetic field. Several effects have been taken into account, in particular the non-eigenstate for th e neutron in each layer and the Larmor precession of the neutron in th e layers which induce a breakdown of the plane-wave approximation. We describe also a new spectrometer built at the reactor Orphee in Saclay in order to perform polarized neutron reflectivity on thin films and magnetic layers with polarization analysis.