Nonequilibrium processes and ferroelectric phase transition in PbGeTe(Ga) crystalsстатья
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Дата последнего поиска статьи во внешних источниках: 18 июля 2013 г.
Аннотация:The impedance of single-crystal samples of PbTe(Ga) and Pb1-xGexTe(Ga) (0less than or equal toxless than or equal to0.095) is investigated in the frequency range from 10(2) to 10(6) Hz and temperature range 4.2-300 K. The temperature dependence of the capacitance of all the Pb1-xGexTe(Ga) samples studied exhibited two types of features. These are a pronounced peak at a temperature T=T-p, caused by a dielectric anomaly at the ferroelectric phase transition, and a characteristic strong frequency dependence of the rise in capacitance in the temperature region T<100 K. The amplitude of the low-temperature effect decreases monotonically with increasing frequency f, and for f>10(5) Hz the effect practically vanishes. This behavior of the capacitance at such low frequencies may be associated with charge exchange processes in the impurity subsystem. The experimentally determined value of T-p is substantially higher than the characteristic temperatures for the appearance of long-term relaxation processes, in particular, the delayed photoconductivity. Consequently, the change of the charge states in the impurity subsystem is not accompanied by dielectric anomalies of the crystal lattice as a whole, and the possible restructuring of the lattice is of a local character. (C) 2004 American Institute of Physics.