The influence of annealing and X-irradiation on the optical anisotropy in incommensurate (N(CH₃)₄)₂ZnCl₄

Abstract

The optical activity, birefringence and the indicatrix rotation of a (001) sample of (N(CH3)4)2ZnCl4 are measured in the high-temperature, incommensurate and partly lock-in phases with a new high-accuracy null polarimeter. The optical properties are shown to be sensitive to the annealing and X-irradiation of a sample via the defect concentration changes. The results can be explained by consideration of a modulated gyration tensor in the incommensurate phase, using the idea of modulation wave distortions imposed by defects.

Simultaneous measurements of crystal optical characteristics of deuterated triglycine sulphate

“…According to formulae (1), the result s ¼ 0 should take place, within the experimental accuracy ((1-3) Â10 À3 in our case). However, the relations (1) represent a sufficient approximation only for transparent, nondichroic crystals and in the absence of multiple light reflection effect [21,22,24]. Otherwise, higherorder corection terms appear in formulae (1), which include the parameters of the latter effects.…”

“…Otherwise, higherorder corection terms appear in formulae (1), which include the parameters of the latter effects. It is most convenient to detect these corrections with just the s parameter [18,21,24]:…”

“…The insert shows the linear fit of e against cot ðD=2Þ for both paraelectric and ferroelectric phases. parency region of DTGS or an apparent consequence of residual anisotropic light scattering, first of all, in the crystal bulk (see [21]). …”

“…Neglecting a scarcely probable in practice situation of temperature-independent though nonzero normal wave ellipticity (see also [21]), one can see from formula (2) that the dependence of e 0 upon cot ðD=2Þ is linear when the gyration is absent. Fig.…”

“…Its working principles and construction of the optical apparatus are in detail described elsewhere (see, e.g., [18,[20][21][22]). According to the method, one measures the linear dependences of the azimuth c and the ellipticity e of the light emergent from a crystal, upon the azimuth q of the incident light, under some additional conditions.…”