Premium
Improvement of the accuracy of HAUP, high‐accuracy universal polarimeter: application to ferroelectric [N(CH 3 ) 4 ]ZnCl 4
Author(s) -
Kobayashi J.,
Kumomi H.,
Saito K.
Publication year - 1986
Publication title -
journal of applied crystallography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.429
H-Index - 162
ISSN - 1600-5767
DOI - 10.1107/s0021889886089197
Subject(s) - phason , polarimeter , ferroelectricity , polarizer , birefringence , phase (matter) , optics , phase transition , tensor (intrinsic definition) , refraction , physics , quadrupole , optical axis , materials science , polarimetry , condensed matter physics , computational physics , dielectric , optoelectronics , mathematics , atomic physics , quantum mechanics , quasicrystal , pure mathematics , scattering , lens (geology)
It is shown that in fixing the crossed Nicols positions a systematic error must invariably be introduced caused by the parasitic ellipticities of the polarizer and analyzer and the refraction of the light beam by the specimen. A method has been derived by which this systematic error can be removed from the original HAUP method. The improved method has been successfully applied to the measurement of the temperature dependence of the gyration‐tensor component g 23 of [N(CH 3 ) 4 ] 2 ZnCl 4 , although it is as small as 10 −7 . The study of optical activity shows directly that the order parameter of the incommensurate phase of the (NH 4 ) 2 SO 4 family is complex and that a phason exists in this phase. It can be shown that the optical activity of the incommensurate phases can be classified into three types, [N(CH 3 ) 4 ] 2 ZnCl 4 corresponding to the case where the nearly commensurate domains are optically active. The extensive usefulness of optical activity to the study of phase transitions is suggested.