Pressure dependence of two-magnon Raman scattering in NiO

We report on the pressure dependence of Raman scattering by magnon pairs in NiO for the range 0–30 GPa. The data are in excellent agreement with Bloch’s empirical law describing the dependence of superexchange on volume. Using Anderson’s theory, we find that the pressure depencence of the antiferromagnetic exchange constant is mainly determined by the hopping parameter of a Hubbard model involving Ni(${\mathit{e}}_{\mathit{g}}$)-O(2p) hybridization. The implications of these results to high-temperature superconductors and early Raman data are discussed.