Optical activity and critical exponent of the order parameter in lead germanate crystals.1.The case of diffused phase transition in Pb5Ge3O11 doped with Cu, Ba and Si ions

Abstract

In the present paper an approach for evaluation of critical exponent of the order parameter at the diffused phase transition is developed on the basis of optical activity data. β =). The critical exponent for the pure lead germanate is also clarified.

On the critical exponent of order parameter in Sn2P2S6 and Sn2P2(Se0.28S0.72)6 crystals

“…As a consequence, the critical exponent can be found only approximately. In solving this problem, we apply the approach developed in the work [19]. Namely, we consider a phase transition diffused due to some scalar inhomogeneity, e.g., scalar defects.…”

Critical exponents of the order parameter of diffuse ferroelectric phase transitions in the solid solutions based on lead germanate: studies of optical rotation

“…We illustrate the ambiguity in the choice of the Curie temperature based on the example of DFEPT in PGO doped with 0.140 wt. % of Cu 2+ ions (PGO:Cu_140), which was studied in our recent work [15]. As seen from figure 1, the temperature dependences of the optical rotation 𝜌 in the PGO:Cu_140 crystals have a sufficiently long "tail", which indicates to the presence of DFEPT.…”

Dispersion of optical activity and absorption in Pb5Ge3O11:Cu2+ crystals

“…Dispersion of the optical rotation has been measured with the aid of polarimetric set-up described in our recent report [9], for the case of normal conditions and the light propagation direction along the optic axis. The absorption spectra have been obtained with a Specord M40 spectrophotometer.…”

“…Here we should mention that the optical activity has been studied mainly for the wavelength of He-Ne laser (λ = 632.8 nm) and the dispersion of the effect has been touched upon only for the pure lead germanate [3]. The recent study [9] …”