Neutron resonance spin echo (NRSE) spectroscopy enables us to measure energytransfer in a neutron scattering process with high energy resolution. It is desirable toapply NRSE spectroscopy to pulsed neutron sources because this application allows avery wide range of the spin echo time. We have developed the neutron resonance spinflipper applicable to a polychromatic pulsed neutron beam, which is necessary for the TOF-NRSE method. Using this flipper, we have also succeeded in observing spin echosignals with polarization higher than 0.65 for the pulsed neutron beam with wavelengthfrom 0.3 to 0.9nm. We discuss those experimental results and the developments for the NRSE spectrometers at a new spallation source.

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Inelastic neutron scattering measurements have been performed to study geometricalspin frustration effects on the magnetism in the fcc antiferromagnet NiS₂. A honeycombpattern of magnetic diffuse scattering along the Brillouin zone boundary was observedup to much higher temperature than T_N indicating a direct evidence for frustratedmagnetism. Theoretical analyses revealed that the system is located very close to thephase boundary between the type-I antiferromagnetic (AF) ordered phase (Q_AF=(1, 0, 0)) and the type II AF ordered phase (Q_AF=(1/2, 1/2, 1/2)). AF long-range order lifts thedegeneracy and gives rise to a spectral shift from a low energy to a finite energy-J.

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