Effect of pressure on magnetic excitations in CoO

Abstract We investigated the effect of high pressure (P ⩽ 17 GPa) on magnetic excitations in CoO by Raman spectroscopy in the temperature range 10–300 K. In addition to the strong lines at 143, 221 and 296 cm−1 observed previously, we also measured weak Raman features at 251, 430 and 486 cm−1, and an asymmetrical broad band centered around 1040 cm−1 arising from magnetic excitations. We propose a single-ion effective Hamiltonian for Co2+ and fit the energy levels of magnetic excitations using approximate second quantization techniques. The antiferromagnetic exchange interaction constant J2 for next-nearest neighbors is found to scale with the bond length d according to d ln J2/d ln d = 8.0±0.5.