Study of vibrational and magnetic excitations in NicMg1 cO solid solutions by Raman spectroscopy

The Raman scattering by phonons and magnons was studied for the first time in the polycrystalline solid solutions Ni c Mg 1− c O. The experimental Raman spectrum for c = 0.9 is similar to that of NiO and consists of six well resolved bands, whose origins are the disorder-induced one-phonon scattering (bands at 400 and 500 cm −1 ), two-phonon scattering (bands at 750, 900, and 1100 cm −1 ), and two-magnon scattering (the broad band at ∼ 1400 cm −1 ). We found that the dependence of the two-magnon band in solid solutions on the composition and temperature is consistent with their magnetic phase diagram. We also observed that the relative contribution of two-phonon scattering decreases strongly upon dilution with magnesium ions and disappears completely at c < 0.5. Such behaviour is explained in terms of a disorder-induced effect, which increases the probability of the one-phonon scattering processes.