Magnetic frustrations in the face centered cubic antiferromagnet NiS2

Neutron scattering experiment on NiS2 single crystal revealed a honeycomb pattern of the intensity distribution in reciprocal lattice space (continuous-line structure along the fcc zone boundary) providing the first direct evidence for nearly frustrated antiferromagnetism (AF) on the face centered cubic (fcc) lattice. A small but finite lattice distortion below 30.9 K lifts the degeneracy of the magnetic ground state due to the frustration and eventually result in the coexistence of the type I and the type II AF long range orderings, which are mutually incompatible in the fcc symmetry at higher temperatures.