Journal of Physical Studies 23(3), Article 3706 [8 pages] (2019) DOI: https://doi.org/10.30970/jps.23.3706 THE EFFECT OF METAL ION SUBSTITUTION ON THE DIELECTRIC DISPERSION IN NH2(CH3)2Ga1-xCrx(SO4)2 · 6H2O CRYSTALS V. Kapustianyk{1,2}, S. Semak{2}, Yu. Eliyashevskyy{2}, S. Sereda{1,3} 1Scientific-Technical and Educational Center of Low Temperature Studies, Ivan Franko National University of Lviv, 50, Drahomanov St., UA-79005, Lviv, Ukraine 2Department of Solid State Physics, Ivan Franko National University of Lviv, 50, Drahomanov St., UA-79005, Lviv, Ukraine 3Forschungszentrum Jülich, Institut für Energie- und Klimaforschung-Plasmaphysik, 52425, J\"ulich, Germany

The comparative study of the dielectric dispersion in the vicinity of the ferroelectric-ferroelastic phase transition in NH$_{2}$(CH$ _{3} $)$ _{2} $Ga$ _{1-x} $Cr$ _{x} $(SO$ _{4} $)$ _{2} $ $ \cdot $ 6H$ _{2} $O ($x=0$; 0.065) crystals was performed. As it follows from the analysis of the temperature-frequency dependences of the dielectric permittivity and the Cole-Cole diagrams, the dielectric dispersion is connected with a critical slowing down of the dipole relaxation (fundamental dispersion) in the high frequency range and with the domain wall dynamics at lower frequencies of the measuring electric field. It has been shown that the metal ion substitution practically does not affect the temperatures of phase transitions but manifests itself in the parameters of the low frequency dielectric dispersion. The substitution of gallium with chromium is followed by an increase in the relaxation time, the activation energy and the half-width of the Gaussian, which describes the distribution of the relaxation times. This was explained by the fact that chromium ions, due to their larger sizes in comparison with gallium ions, cause local lattice deformations. The latter promote the formation of more massive dipole clusters in the vicinity of the ferroelectric phase transition.

PACS number(s): 77.84.-s, 77.80.B-, 77.22.Gm, 75.78.Fg

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