Spin dynamics in NiO near and above the Neel temperature

Measurements of the inelastic magnetic scattering from a single crystal NiO have been carried out in order to obtain the paramagnetic χ(q) i.e., the spin correlation above the Neel temperature. It has been found that rather intense paramagnetic scattering exists in the energy region of ℎω-20meV and is almost unchanged up to T=623 K. The intensity is concentrated near the antiferromagnetic zone center, indicating the existence of the significant instantaneous antiferromagnetic correlations above TN. Another strongly temperature-dependent inelastic scattering, which shows the critical behaviour, has been found at ℎω≤4meV. (author)