Abstract
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 TN 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 (QAF=(1, 0, 0)) and the type II AF ordered phase (QAF=(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.
