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Dielectric and Dilatometric Properties of NH(CH_3)_3CuCl_3·2H_2O Low Dimensional Ferroics

100%

Korchak Y., Kapustianik V., Batiuk A., Girnyk I., Czapla Z., Dacko S.

Acta Physica Polonica A

2004

vol. 106

issue 1

39-49

On the basis of dilatometric and dielectric investigations of NH(CH_3)_3CuCl_3·2H_2O crystals the earlier unknown phase transition with considerable temperature hysteresis was found at T_1^c=198 K and T_1^h=223 K, respectively, in cooling and heating runs. Existence of the characteristic dielectric dispersion was revealed within the high-temperature phase. It corresponds to the single dielectric relaxator below 250 K as well as to co-existence of two relaxators above this temperature. The determined values of the activation energy and relaxation time are characteristic of the co-operative reorientation of the trimethylammonium cation (high-frequency relaxator) whereas the combined reorientation motions of the CuCl_2·2H_2O chains would be responsible for the low-frequency relaxation process. It was found that the above mentioned quasi-Debye type processes are involved into the mechanisms of the protonic conductivity.

Dielectric and Birefringent Properties of [(CH_3)_2NH_2]_5Cd_2CuCl_{11} Solid Solutions in the Region of Their Phase Transitions

100%

Eliyashevskyy Y., Kapustianyk V., Dacko S., Czapla Z., Batiuk A., Sveleba S.

Acta Physica Polonica A

2006

vol. 109

issue 2

171-178

On the basis of the optical and dielectric investigations of [(CH_3)_2NH_2]_5Cd_2CuCl_{11} solid solutions the existence of phase transitions at T_1=175 K and T_2=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" [(CH_3)_2NH_2]_5Cd_3Cl_{11} crystals. It was found that the proton conductivity in [(CH_3)_2NH_2 ]_5Cd_2CuCl_{11} crystals is realized through the Grotthus mechanism. The investigations of the birefringent properties confirmed existence of the structural changes at T_0=320 K connected with the complex co-operative effect involving weakening of the hydrogen bonds and modification of the Jahn-Teller distortion with temperature.

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2 Acta Physica Polonica A

1 2006

1 2004

2 Batiuk A.

2 Czapla Z.

2 Dacko S.

1 Eliyashevskyy Y.

1 Girnyk I.

1 Kapustianik V.

1 Kapustianyk V.

1 Korchak Y.

1 Sveleba S.

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Dielectric and Dilatometric Properties of NH(CH_3)_3CuCl_3·2H_2O Low Dimensional Ferroics

Dielectric and Birefringent Properties of [(CH_3)_2NH_2]_5Cd_2CuCl_{11} Solid Solutions in the Region of Their Phase Transitions