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The electrogyration effect is the spatial dispersion phenomenon, that consists in the change of optical activity (gyration) of crystals by a constant or time-varying electric field. Being a spatial dispersion effect, the induced optical activity exhibit different behavior under the operation of wave vector reversal, when compared with the Faraday effect: the optical activity increment associated with the electrogyration effect changes its sign under that operation, contrary to the Faraday effect. Formally, it is a special case of gyroelectromagnetism obtained when the magnetic permeability tensor is diagonal.〔() Prati E. (2003) "Propagation in gyroelectromagnetic guiding systems", ''J. of Electr. Wav. and Appl.'' 17, 8, 1177〕 The electrogyration effect linear in the electric field occurs in crystals of all point groups of symmetry except for the three cubic – m3m, 432 and . The effect proportional to the square of the electric field can exist only in crystals belonging to acentric point groups of symmetry. == The historical background of discovery of electrogyration == The changes in the optical activity sign induced by the external electric field have been observed for the first time in ferroelectric crystals LiH3(SeO4)2 by H. Futama and R. Pepinsky in 1961 ,〔() Futama H. and Pepinsky R. (1962) "Optical activity in ferroelectric LiH3(SeO3)2", ''J. Phys. Soc. Jap.'' 17, 725〕 while switching enantiomorphous ferroelectric domains (the change in the point symmetry group of the crystal being 2/m«m). The observed phenomenon has been explained as a consequence of specific domain structure (a replacement of optic axes occurred under the switching), rather than the electrogyration induced by spontaneous polarization. The first description of electrogyration effect induced by the biasing field and spontaneous polarization at ferroelectric phase transitions has been proposed by K. Aizu in 1963 on the basis of third-rank axial tensors 〔() Aizu K. (1964) “Reversal in optical rotatory power – “gyroelectric” crystals and “hypergyroelectric” crystals”, Phys. Rev. 133 (6A) A1584–A1588〕 (the manuscript received on September 9, 1963). Probably, K. Aizu has been the first who defined the electro-gyration effect (”the rate of change of the gyration with the biasing electric field at zero value of the biasing electric field is provisionally referred to as “electrogyration””) and introduced the term “electrogyration” itself. Almost simultaneously with K. Aizu, I.S. Zheludev has suggested tensor description of the electrogyration in 1964 〔() Zheludev I.S. (1964), "Axial tensors of the third rank and the physical effects they describe", ''Kristallografiya'' 9, 501-505.(''Sov.Phys.Crystallogr.'' 9,418 )〕 (the manuscript received on February 21, 1964). In this paper the electrogyration has been referred to as “electro-optic activity”. In 1969, O.G. Vlokh has measured for the first time the electrogyration effect induced by external biasing field in the quartz crystal and determined the coefficient of quadratic electro-gyration effect 〔() Vlokh O.G.(1970). "Electrooptical activity of quartz crystals", ''Ukr.Fiz.Zhurn.''15(5), 758-762.(O.G. (1970). "Electrooptical activity of quartz crystals", ''Sov.Phys. Ukr.Fiz.Zhurn.''15, 771. )〕 (the manuscript received on July 7, 1969). Thus, the electrogyration effect has been predicted simultaneously by Aizu K. and Zheludev I.S. in 1963–1964 and revealed experimentally in quartz crystals by Vlokh O.G. in 1969.〔 .〔() Vlokh O.G. (1971) "Electrogyration effects in quartz crystals", ''Pis.ZhETF.'' 13, 118-121 (O.G. (1971) "Electrogyration effects in quartz crystals", ''Sov.Phys. Pis.ZhETF.'' 13, 81-83. )〕〔() Vlokh O.G. (1987), "Electrogyration properties of crystals" ''Ferroelectrics'' 75, 119-137.〕〔() Vlokh O.G. (2001) "The historical background of the finding of electrogyration", ''Ukr.J.Phys.Opt.'', 2(2), 53-57〕 Later in 2003, the gyroelectricity has been extended to gyroelectromagnetic media,〔 which account for ferromagnetic semiconductors and engineered metamaterials, for which gyroelectricity and gyromagnetism (Faraday effect) may occur at the same time. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Electro-gyration」の詳細全文を読む スポンサード リンク
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