PRISM, the new polarized neutron reflectometer with polarization analysis at the LLB

Abstract

The technique of neutron reflectivity emerged less than 15 years ago. It has appeared as a key technique in the study of polymers and magnetic thin films. In the last ten years, neutron reflectivity has successfully been applied to the study of magnetic multilayers and ultrathin films [1]. Problems such as the magnetic ordering in rare-earth multilayers [2], surface magnetism, and anisotropy in ultrathin magnetic layers [3] have found answers. However, in order to push the possibilities of neutron reflectivity further, it has appeared that improvements in the flux were necessary. In that aim, we have recently built a new polarized reflectometer with polarization analysis dedicated to the study of magnetic thin films at the Laboratoire Léon Brillouin. We have used different ways to increase the available neutron flux: • increase of the wavelength spectrum width δλ/λ by using a multilayer monochromator (compared to the very high resolution δλ/λ = 0.6 percent of a graphite monochromator); • focalization of a 100 mrn high neutron beam onto a 15 mm high region (which is suitable for the study of small magnetic samples); and • use of a position sensitive detector (measurement of both spin states at the same time and access to off- specular measurements).