Influence of Partial Metal Ion Substitution on the Temperature Evolution of the Optical Absorption Edge in ((CH3)2CHNH3)4Cd3Cl19:Cu Crystals

V. Kapustianyka, b, P. Yonakb, V. Rudyka, Z. Czaplac, d, R. Cachd aScientific-Technical and Educational Center of Low-Temperature Studies, Ivan Franko National University of Lviv, Dragomanova Str. 50, 79005 Lviv, Ukraine bDepartment of Physics, Ivan Franko National University of Lviv, Dragomanova Str. 50, 79005 Lviv, Ukraine cDepartment of Physics, Opole University of Technology, Ozimska 75, 45-370 Opole, Poland dInstitute of Experimental Physics, University of Wrocław, Pl. M. Borna 9, 50204 Wrocław, Poland

Received: February 14, 2019; revised version April 19, 2019; in final form April 23, 2019

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On the basis of absorption spectroscopy data the temperature evolution of the optical absorption edge in the region of phase transitions of [(CH3)2CHNH3]4Cd3Cl10 (IPACC) and the same crystal doped with Cu2+ (IPACCC) was studied. Performed investigations ascertained a noticeable influence of the doping with Cu2+ ions on the exciton-phonon interaction and respectively on the shape and temperature evolution of the optical absorption edge of IPACC crystals. It has been found that characteristic parameters of Urbach's rule show anomalous behaviour at the phase transition point T2=293 K. It was shown that the low energy tail of the charge transfer band in IPACCC is formed with participation of the internal vibrations of the metal-halogen complex. On the other hand, the low energy tail of the fundamental edge for both IPACC and IPACCC is formed with participation of the internal vibrations of the metal-halogen complex or skeletal (or translational) vibration of IPA cation.

DOI:10.12693/APhysPolA.136.208 topics: transition metal, charge transfer, optical spectroscopy, crystal and ligand fields, phase transitions, exciton-phonon interaction, Urbach's rule