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Electrogyration effect in lead germanate crystal family.
2. The case of crystals doped with Li, Eu, La, Nd and (Li, Bi)
1Shopa Y.I., 1Kushnir O.S., 2Adamenko D., 1Shopa R.Y., 1Dzyubanski V.S., 2Vlokh R.O., 2Vlokh O.G.

1Lviv Ivan Franko National University, 8 Kyrylo and Mefodiy St.,  79005 Lviv, Ukraine
2 Institute of Physical Optics, 23 Dragomanov St., 79005 Lviv, Ukraine, E-mail: vlokh@ifo.lviv.ua 

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Temperature dependences of spontaneous and induced electrogyration are studied for the crystals of lead germanate doped with Li, Eu, La, Nd and (Li, Bi). Critical fluctuations observed in the optical parameters near ferroelectric phase transition point are explained in frame of the first fluctuation correction to the Landau theory and the critical indices governing the order parameter are found. It is shown that the doped crystals may be promising for practical applications owing to their large induced electrogyration coefficients

Keywords: lead germanate crystals, ferroelectric phase transition, optical activity, electrogyration, critical fluctuations

PACS: 42.25.Bs, 87.15.Mi, 87.64.Ni
Ukr. J. Phys. Opt. 10 71-81 
doi: 10.3116/16091833/10/2/71/2009
Received: 17.02.2009
 

Анотація. У роботі вивчено температурні залежності спонтанної та індукованої електрогірації кристалів германату свинцю з домішками Li, Eu, La, Nd і (Li, Bi). Спостережувані в оптичних параметрах критичні флуктуації поблизу точки сегнетоелектричного фазового переходу пояснено в рамках підходу першої флуктуаційної поправки до теорії Ландау. Визначено критичні індекси параметра порядку. Показано, що леговані кристали перспективні для практичних застосувань завдяки великим коефіцієнтам індукованої електрогірації.
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