[en] Perpendicular magnetic-field transitions of pure Sn films, assessed by microwave absorption measurement as a function of specimen thickness (65 nm-200 μ) and temperature (1.5 K-Tmc) are presented. The passage from intermediate- to mixed-state behaviour was observed. The values obtained for the critical thickness d perpendicular at which the passage from type-I to type-II behaviour occurs agree with theoretical predictions. Critical perpendicular megnetic field values, H perpendicular, also agree well with theoretical predictions for d< d perpendicular and in the limit d>>d perpendicular

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[en] The use of nuclear-spin polarized ³He as a spin filter for low energy neutron beams is discussed and many properties of these polarizers are described. We compare this technique to other methods for polarizing neutrons of energy 0.01-100 eV. The status of a joint IUCF/NIST project for constructing transmission polarizers using both Rb spin-exchange and metastability-exchange optical pumping is presented. (orig.)