Phonon-Induced Spin-Dependent Infrared Absorption in KNiF₃

抄録

A temperature-dependent absorption band was observed in the infrared region for KNiF₃ below the Néel temperature (T_N=275°K). The peak is located at 1230 cm⁻¹ at 100°K and shifts to the longer wave-length side with increasing temperature. This band can be attributed to a phonon-induced electric dipole transition of the spin system which has been discussed by Mizuno and Koide. The exchange parameter for KNiF₃ is determined from the peak position to be J=52.3°K or 55.3°K.