An infrared spectroscopic study of the low-spin to intermediate-spin state((1)A(1)-T-3(1)) transition in rare earth cobaltates, LnCoO(3) (Ln = La, Pr and Nd)

Low-spin (LS) to intermediate-spin (IS) state transitions in crystals of Ln CoO(3) (Ln = La, Pr and Nd) have been investigated by variable temperature infrared spectroscopy. The spectra reveal the occurrence of the transition around 120, 220 and 275 K, respectively, in LaCoO3,PrCoo(3) and NdCoO3, at which temperatures the intensities of the stretching and the bending modes associated with the LS state decrease, accompanied by an increase in the in tensities of the bands due to IS state. The characteristic frequencies of b oth the spin states decrease with increase in temperature, showing anomalie s around the transition. (C) 2001 Published by Elsevier Science B.V.