Dielectric and Birefringent Properties of [(CH3)2NH2]5Cd2CuCl11 Solid Solutions in the Region of Their Phase Transitions

Yu. Eliyashevskyya, V. Kapustianyk b, S. Dacko a, Z. Czapla a, A. Batiuk b and S. Svelebab aInstitute of Experimental Physics, University of Wrocław, pl. M. Borna 9, 50-204 Wrocław, Poland bLviv Ivan Franko National University, Scientific-Technical and Educational Center of Low Temperature Studies, Dragomanova St. 50, 79005, Lviv, Ukraine

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Received: 6 06 2005; revised version: 10 10 2005; in final form: 29 11 2005;

On the basis of the optical and dielectric investigations of [(CH3)2NH2]5Cd2CuCl11 solid solutions the existence of phase transitions at T1=175 K and T2=117.5 K was confirmed. Both phase transitions were found to be shifted toward lower temperatures with respect to the corresponding transitions in the "host" [(CH3)2NH2]5Cd3Cl11 crystals. It was found that the proton conductivity in [(CH3)2NH2 ]5Cd2CuCl11 crystals is realized through the Grotthus mechanism. The investigations of the birefringent properties confirmed existence of the structural changes at T0=320 K connected with the complex co-operative effect involving weakening of the hydrogen bonds and modification of the Jahn-Teller distortion with temperature.

DOI: 10.12693/APhysPolA.109.171 PACS numbers: 65.40.-b, 77.22.Ch