Indofluorides in the AMF3–InF3 systems (A=K, Rb, Cs and M=Mg, Zn) and optical properties of Cr3+:K0.38Mg0.38In0.62F3

Among the fluorides disclosed in the AMF3–InF3 systems (A=K, Rb, Cs/M=Mg, Zn), the most favorable material for optical applications in relation with the optical quality of its crystals is K0.38Mg0.38In0.62F3 (KMI), a distorted monoclinic Magnéli-bronze, which crystals are grown from the melt. Cr3+ introduced in this host is optically characterized by optical spectroscopy. The chromium ions in the single crystals occupy simultaneously centrosymmetric and non-centrosymmetric sites. The broad emission band (4T2 g→4A2 g transition) obtained in the near infrared range is characteristic of a small crystal field effect (Dq=1476 cm−1). Crystal field analysis leads to a very good agreement between calculated and experimentally observed energy levels. Furthermore, dips observed in the absorption at about 15370 cm−1 are related to the calculated mixing between the wave functions, connected with the 4T2 g (4F) and 2Eg (2G) and 2T1 g (2G) electronic levels.