Temperature behaviour of optical phonons near Tc in triglycine sulphate and triglycine selenate

Winterfeldt, V.; Schaack, G.; Kloopperpieper, A.

doi:10.1080/00150197708236717

Cited by 70 publications

(12 citation statements)

References 29 publications

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“…A similar situation has been encountered in TGS (Winterfeldt and Schaack 1977). There it was concluded that the additional symmetry elements in the high-temperature phase are only pseudo-elements, i.e.…”

Section: Synopsissupporting

confidence: 62%

“…These are the so-called hard-core modes. This type of behaviour has been encountered in other systems previously before (tri-glycine sulphate (TGS), TGSe, thiourea, Rochelle salt) and has been attributed to a non-linear pseudo-spin-phonon coupling (Winterfeldt and Schaack 1977, Winterfeldt 1980. The linewidths in both the infrared and Raman spectra increase considerably with T. As a consequence, weak lines that are well resolved at 2 K disappear rapidly with increasing temperature, while other lines merge with neighbouring lines, producing the appearance of broad bands in the high-temperature spectra.…”

Section: Synopsissupporting

confidence: 60%

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Chemical Dynamic Behavior at Solid Surfaces

Tamaru

1993

Jpn. J. Appl. Phys.

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We report infrared and Raman spectroscopic investigations of single crystals of tris-sarcosine calcium chloride (TSCC), of the isomorphous tris-sarcosine calcium bromide (TSCB) and of mixed crystals with different chlorine-bromine concentration ratios x (for TSCC, -rBJ in the whole wavenumber region below4000 cm-' and in a temperature interval 2 K S T S 170 K. A general survey of the Raman and infrared reflection spectra is given and their temperature and concentration dependences are discussed. We concentrate on three different soft modes observed only in the ordered phase and on several 'hard-core' modes, which can be found in different spectral regions and which demonstrate a temperaturedependent frequency renormalisation of the phonons on approaching T;.One of the soft modes is Raman-active with a negligible LGTO splitting; the other two soft modes appear in the infrared spectrum with a small LO-TO splitting. Contrary to the usual behaviour of polar soft modes the LO frequencies also soften. The temperature and concentration dependences of these three modes are presented in detail. They are correlated with the presence of three different lattice sites for the sarcosine molecules in the lowtemperature phase. The contribution of the soft modes to the anomaly of the dielectric constant at low frequencies is calculated and it is found that the displacive behaviour is of minor importance as compared with the order-disorder contribution to the character of the structural phase transition in TSCC.A microscopic order parameter is proposed that supports the assumption of a pseudoproper phase transition in TSCC.

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Section: Synopsissupporting

confidence: 62%

Section: Synopsissupporting

confidence: 60%

Chemical Dynamic Behavior at Solid Surfaces

Tamaru

1993

Jpn. J. Appl. Phys.

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“…The crystal orientation was established by the well developed faces (OOl), (OlO), (110), and (120). To obtain the Raman spectra, standard techniques were used, which are described in [4]. Because of the dehydration of the crystal in vacuum all experiments in the temperature region from -25 to 28 "C were made within a non-evacuated cryostat.…”

Section: Experimental Methods and Resultsmentioning

confidence: 99%

Raman Spectroscopic Investigation of Ferroelectric Phase Transitions in Rochelle Salt

Winterfeldt

1980

Physica Status Solidi (b)

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Raman scattering spectra of single crystals of Rochelle salt are recorded a t 2 K and a t several temperatures between 248 and 300 K in the spectral region from 0 to 4000 cm-l. The frequencies of some phonon modes soften or harden in the intermediate ferroelectric phase between the two Curie points which are known to exist in this material. I n the paraelectric phases the frequencies remain constant. This behaviour can be explained by applying a simple nonlinear pseudospinphonon coupling theory originally developed for the TGS family and the incommensurate phase transition in thiourea. The anomalous specific heat due to temperature-dependent optical phonon modes is also discussed. Es werden die Ramanspektren von Rochellesalz-Einkristallen

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“…A large number of vibrational studies on TGS are reported, including the lowtemperature and low-frequency spectra (Barker and Tinkham 1963;Quilichini et al, 1969;Koneko et al, 1974;Cerevenka et al, 1976;Schaack and Winterfeldt, 1977;Winterfeldt et al, 1977;Huong and Hilczer 1981;Komyak et al, 1993;Santra et al, 1994;Malyarevich and Posledovich 1996). Quilichini et al (1969) measured the temperature dependence of polarized Raman spectra below 200 cm À1 , but failed to see significant spectral changes due to the phase transition.…”

Section: Introductionmentioning

confidence: 95%

Effect of alanine doping on the low-frequency Raman Modes in triglycine sulphate crystals at 12 K

et al. 2003

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Low-temperature Raman spectra of pure, and alanine doped triglycine sulphate (TGS) crystals in the lowfrequency range <400 cm À1 are reported. Substantial changes in the relative intensity of several modes occur whereas the band positions remain largely unchanged. Doping induced relative intensity changes are correlated with the change in H-bonding and molecular reorientation. Results indicate that alanine replaces G(I) mainly at low-dopant concentration. However, doping causes reorientation of all the three ions.

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Temperature behaviour of optical phonons near Tc in triglycine sulphate and triglycine selenate

Cited by 70 publications

References 29 publications

Chemical Dynamic Behavior at Solid Surfaces

Chemical Dynamic Behavior at Solid Surfaces

Raman Spectroscopic Investigation of Ferroelectric Phase Transitions in Rochelle Salt

Effect of alanine doping on the low-frequency Raman Modes in triglycine sulphate crystals at 12 K

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