Pressure effects on first-order magnetic Raman scattering in NiO

The pressure dependence of first-order magnetic Raman peak of NiO single crystal was studied up to 20 GPa at room temperature. At ambient pressure, an unknown peak is also observed at nearly the same position as the one-magnon one and their separation becomes remarkable with increasing pressure. Pressure coefficients of the one-magnon peak and the other peak are obtained as 0.4 and 1.5 cm−1 GPa−1, respectively. The next-nearest-neighbour antiferromagnetic exchange constant J2 is obtained as a function of the lattice constant.