Some observations on polarized neutron reflectivity in applied fields

Unpolarized neutron reflectivity measurements on FeCo/Pt and Fe/Co superlattices have revealed a number of interesting features when a relatively large field was applied normal to the samples' surface. Some of the features, which include oscillations and Yoneda scattering below the critical edge, can be understood by calculating the polarization-dependent reflectivities and transmissions of the samples. Measurements with polarization analysis, however, show that the Zeeman-split reflected beams, expected in reflectivity experiments in an applied magnetic field, do not appear to have a unique spin state. The interpretation of the data is believed to lie in a non-collinearity between the axis for the reflected neutron beam polarization and the axis for the polarization analysis