EXPERIMENTS WITH NEUTRON POLARIZATION ANALYSIS

Neutron polarization analysis experiments of the past 25 years are rev iewed. In that time the technique has progressed from a curiosity to b eing a useful tool to be used when needed. In early experiments, the p olarization of the scattered beam was analysed in the same direction a s the polarization of the incident beam but, in some later experiments , full three-dimensional polarization analysis has been employed. This article starts by writing down the interactions which the neutron has with condensed matter and deriving the cross-sections for scattering and final polarizations of the scattered beam. This is done displaying the spin state functions of the neutron explicitly. A variety of expe riments is then reviewed, commencing with the elastic and inelastic sc attering experiments performed by Moon, Riste Koehler in the late 1960 s. Elastic scattering experiments where it is important to separate nu clear and magnetic cross-sections such as antiferromagnetic defect sca ttering are reviewed together with separation out of the nuclear spin scattering for various purposes. Of particular interest are the fully three-dimensional analysis experiments which reveal more about the str ucture and domain populations of certain antiferromagnets. Inelastic e xperiments for which polarization analysis is vital are those on param agnets at high temperatures where it is necessary to discriminate agai nst phonon scattering. Spin glasses are treated as frozen paramagnets Polarization analysis also has another role to play in the separation of magnetic modes in both paramagnets and ordered magnets, and several of these experiments are reviewed. Finally it is possible to tag the polarization of a neutron beam in time and space and to measure the re sult at another time and place and this through various techniques yie lds information about the change in neutron energy on scattering. The techniques of pseudo-random flipping time of flight, neutron spectral modulation and neutron spin-echo spectroscopy are briefly reviewed but the techniques of polarized-neutron-beam management are left to anoth er review.