The technique of longitudinal neutron polarization analysis on a multi-detector neutron spectrometer (so-called 'xyz'-polarization analysis) is presented. This technique allows the simultaneous and unambiguous determination of the nuclear, magnetic and nuclear spin-incoherent scattering cross sections as a function of both momentum transfer and energy transfer. The implementation of xyz-polarization analysis on the recently upgraded D7 spectrometer at the Institut Laue-Langevin in Grenoble is described. Several examples of neutron polarization analysis studies of disordered systems on D7 are given, illustrating the valuable information which can be retrieved from the analysis of neutron diffraction patterns between the Bragg peaks. ‡ Current address: ISIS Facility, Rutherford Appleton Laboratory, Didcot, UK. research papers J. Appl. Cryst. (2009). 42, 69-84 J. R. Stewart et al. Disordered materials studied using neutron polarization analysis 71 research papers 80 J. R. Stewart et al. Disordered materials studied using neutron polarization analysis

The results of elastic, quasielastic, and inelastic neutron-scattering studies on polycrystalline CeM2Ge2 (M=Ag, Au, and Ru) are presented. All compounds reveal long-range magnetic order at low temperatures. Ferromagnetic (M=Ru), antiferromagnetic (M=Au), and incommensurate (M=Ag) structures were detected. Using time-of-flight (TOF) techniques, the crystalline electric-field splittings were determined. With high-resolution TOF experiments the temperature and wave-vector dependence of the magnetic relaxation rate was studied. Korringa-like behavior was found for the Au and Ru compounds.In CeAgzGe2 the temperature dependence of the magnetic relaxation rate exhibits a square-root dependence at high temperatures and shows a residual linewidth for low T. This behavior can be explained by strong hybridization effects of the f electrons with the delocalized band states which are active in heavy fermion systems. Previous results in CeCu2Ge2 and CeNi&Ge& are included, whenever necessary. Detailed comparison is made with results obtained in the disilicides.

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A favored interpretation of the gamma <--> alpha phase transition in cerium postulates the transformation of the localized 4f state in gamma-Ce to a weakly correlated itinerant 4f band in alpha-Ce. However, results of high-energy neutron inelastic scattering measurements, presented here, show clearly that the magnetic susceptibility response from alpha-Ce follows the Ce3+ form factor despite the large, 30-fold, increase in its spectral width relative to that in gamma-Ce. This observation provides, for the first time, indisputable evidence for the localized character of the 4f state in the alpha phase. The present findings appear consistent with recent calculations combining dynamical mean-field theory with the local density approximation that indicate a strongly correlated 4f state in alpha-Ce. The localized 4f state is also fundamental to the Kondo volume collapse theories for the gamma <--> alpha phase transition in cerium.

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