One-and two-magnon contributions in optical spectra of KNiF3 single crystal

Abstract The one-magnon (1M) and two-magnon (2M) contributions were studied in optical absorption spectra of KNiF3 single crystal, measured in the temperature range from 5 K to 300 K. The three absorption bands were considered in details. The first band is due to the magnetic-dipole transition3 A2g(F) → 3T2g(F), centred at 7700 cm−1, and contains the Brillouin zone-centre one-magnon contribution with the energy ω1M = 25 ± 5 cm−1. The other two bands are due to the electric-dipole transitions 3A2g(F) → 1Eg(D) and 3A2g(F) → 1Eg(G), centred at 16000 cm−1 and 31200 cm−1, respectively. Both bands contain the Brillouin zone-boundary two-magnon contribution with the energy ω2M = 813 ± 10 cm−1.