Tris-sarcosine Calcium Chloride Research Articles

The Influence of Quantum Effects on the Ferroelectric Properties of TSCC‐Type Single Crystals

AbstractExperimental investigations on tris‐sarcosine calcium chloride (TSCC)‐type crystals reveal that pure TSCBr and TSCJ are quantum paraelectrics. Measurements of the concentration dependence of phase transition temperature and order parameter, of the pressure dependence of phase transition temperature and of the shift of permittivity peak due to an external electric field show a pronounced influence of quantum fluctuations on the behaviour of these crystals. Based on the model of coupled anharmonic oscillators it is possible to describe all essential ferroelectric properties of the crystal system using only few model parameters in consistent manner. The proposed model can be successfully applied to other quantum paraelectrics.

Brillouin scattering near the ferroelectric phase transition in TSCC

Abstract Brillouin spectra from longitudinal phonons in ferroelectric tris-sarcosine calcium chloride (TSCC) propagating along [100], [010] and [001] have been measured as functions of temperature. Large anomalies were found in the Brillouin shift and linewidth in the [100] and [001] phonons. These anomalies are interpreted as arising from the linear coupling of the polarization and phonons. From the the temperature where the linewidth is maximum, the relaxation time of the polarization fluctuations is estimated to be τ = 3.1×10−12/(Tc−T) sec, where Tc is the ferroelectric transition temperature. We also observed anomalies in Brillouin shift and linewidth of the [010] phonons which propagate along the ferroelectric axis. These anomalies are interpreted as coming from electrostrictive coupling. The energy relaxation time was estimated to be τE=2.5×10−10/(T−Tc) sec in the paraelectric (PE) phase and τE=1.0x10−9/(T−Tc) sec in the ferroelectric (FE) phase, by comparing our Brillouin results with those f the u...

Critical anomalies in EPR spectra near the ferroelectric phase transition in tris-sarcosine calcium chloride crystals

A comparative EPR study with various paramagnetic probes of iron-group elements has been carried out on the ferroelectric phase transition in tris-sarcosine calcium chloride (TSCC) crystals. These ions have yielded complementary results, and one probe was found to be insufficient to obtain necessary information about the transition mechanism. While the soft-mode vector is inferred from the VO++ spectra, either Cr+++ or Fe+++ ions are best suited to observe the critical phenomena near the transition temperature (Tc ~ 130 K). A critical broadening above Tc and an asymmetrical splitting below Tc are observed in the Cr+++ and Fe+++ spectra. The Mn++ spectra are unique in that the order–parameter fluctuation appears only slightly in the line widths above Tc, while the critical region below Tc is characterized by the coexistence of para- and ferroelectric phases. The critical slowing-down effect in the EPR line widths is found to be consistent with that observed in dielectric measurements, suggesting that sarcosine dipoles in TSCC crystals are associated with the elementary dipole for spontaneous polarization.

Concentration and temperature dependences of the order parameter and the soft optic mode of the solid solution TSCC and TSCB

The concentration and temperature dependences of the order parameter in single crystals of the solution trissarcosine calcium chloride 1− x bromide x are studied experimentally by measurements of the EPR line splitting δ H( x, T) and P-E hysteresis loops. The model of coupled anharmonic oscillators in the displacive regime with randomly disordered single site potentials is used to calculate the temperature and concentration dependences of the order parameter and the soft optic mode. It is shown that TSCB may be considered to be an incipient ferroelectric.

Brillouin scattering study of the ferroelectric phase transition in tris-sarcosine calcium chloride.

Brillouin spectra from longitudinal phonons in ferroelectric tris-sarcosine calcium chloride propagating along [100], [010], and [001] have been measured as functions of temperature. Large anomalies were found in the Brillouin shift and linewidth in the [100] and [001] phonons. These anomalies are interpreted as arising from the linear coupling of the polarization and the phonons. From the temperature where the linewidth is maximum, the relaxation time of the polarization fluctuations is estimated to be \ensuremath{\tau}=3.1\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}12}$/(${T}_{c}$-T) sec, where ${T}_{c}$ is the ferroelectric transition temperature. We also observed anomalies in Brillouin shift and linewidth of the [010] phonons which propagate along the ferroelectric b axis. These anomalies are interpreted as coming from electro- strictive coupling. The energy-relaxation time was estimated to be ${\ensuremath{\tau}}_{E}$=2.5\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}10}$/(T-${T}_{c}$) sec in the paraelectric phase and ${\ensuremath{\tau}}_{E}$=1.0\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}9}$/(${T}_{c}$-T) sec in the ferroelectric phase, by comparing our Brillouin results with those of the ultrasonic measurements.

Pressure Dependence of the Raman Spectra of TSCC

We have studied the polarized Raman spectra of tris-sarcosine calcium chloride under hydrostatic pressure (p<500 MPa) at low temperatures (100 K<T<180 K). The pressure and temperature-dependence of the soft mode in the ferroelectric phase near Tc has been determined, the spectra have been fitted to a damped harmonic-oscillator model and to a correlation function derived from a coupled pseudospin-phonon model assuming an order-disorder type transition.

Spectroscopic investigation of the ferroelectric phase transition in tris-sarcosine calcium chloride: an order-disorder system with displacive features. II. Soft modes in pseudo-spin-phonon coupled systems

For pt.I see ibid., vol.17, p.3801 (1984). A model is developed for the softening of an optical phonon of frequency omega 0 due to its interaction with a fast relaxator (a pseudo-spin of relaxation time tau 0< omega 0-1). The short relaxation time of the pseudo-spin is achieved by thermally activated crossing of the barrier in a double-minimum potential starting from an excited vibrational level (vibration-enhanced barrier crossing). For comparison with Raman spectroscopic measurements of this soft mode the classical pseudo-spin and displacement correlation functions are calculated following the work of Yamada and co-workers (1974). The results are applied to the soft modes observed in tris-sarcosine calcium chloride (TSCC) and in various solid solutions of the brominated compound (TSCC1-xBx, O<or=x<or=0.7). The parameters obtained by fits of the correlation functions to the observed lineshapes are very reasonable. The relaxation time obtained compares favourably with the value determined from dielectric measurements.

Spectroscopic investigation of the ferroelectric phase transition in tris-sarcosine calcium chloride: an order-disorder system with displacive features. I. Experimental results

The authors 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 TSCC1-xBx) in the whole wavenumber region below 4000 cm-1 and in a temperature interval 2K&lt;or=T&lt;or=170 K. A general survey of the Raman and infrared reflection spectra is given and their temperature and concentration dependences are discussed. They 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 temperature-dependent frequency renormalization of the phonons on approaching Tc -. One of the soft modes is Raman-active with a negligible LO-TO 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 low-temperature phase. The contribution of the soft modes to the anomaly of the dielectric constant at low frequencies is calculated. A microscopic order parameter is proposed that supports the assumption of a pseudo-proper phase transition in TSCC.

Logarithmic correction to the specific heat in tris-sarcosine calcium chloride

Specific heat experimental results in the 3x10 −2 ≦ | t | ≦5.5x10 −5 temperature range ( t = (T−T C) T C ) were fitted by means of the logarithmically corrected Landau theory of uniaxial dipolar ferroelectrics. The non-universal parameters b and t O as well as the transverse and longitudinal correlation lengths at zero temperature are determined.

Temperature and pressure dependence of dielectric properties of iodinated trissarcosine calcium chloride

The dielectric properties such as the permittivity epsilon , the dielectric loss tangent and the spontaneous polarisation Ps of iodinated trissarcosine calcium chloride were measured at various pressures up to 9 kbar. The peak of epsilon is depressed and broadened by the large internal bias field Eb. The P-E hysteresis loop is highly biased. With increasing I concentrations x, both the peak value of epsilon and the value of Ps decrease rapidly. The ferroelectric transition temperature Tc(x) decreases with increasing x according to the relation (Tc(x)/Tc(0))2=(1-x/xc) where xc is the critical concentration and is estimated as 0.25. The Tc increases greatly with increasing p while the Ps is almost independent of p. The triple point (paraelectric-ferroelectric-new phase) shifted towards higher pressures and lower temperatures with increasing x. The effect of substitution of I for Cl on the dielectric properties is more remarkable than that of Br for Cl.

Logarithmic correction of the susceptibility in tris-sarcosine calcium chloride (TSCC)

Abstract The dielectric constant and loss of tris-sarcosine calcium chloride have been measured in the paraelectric phase. Over more than two orders of magnitude of reduced temperature, the dielectric constant follows accurately the logarithmically corrected mean-field behavior of uniaxial dipolar ferroelectrics. Closer to the transition there is a region possibly dominated by defect-induced losses.

Millimeter wavelength spectroscopy of the ferroelectric phase transition in tris-sarcosine calcium chloride

Abstract We have measured the soft mode responsible for the ferroelectric phase transition in tris-sarcosine calcium chloride: (CH3 NHCH2 COOH)3 CaCl2, by both far infrared and Raman techniques. In the ferroelectric C9 2v phase the soft TO varies from 30. 5 cm−1 at 4K to 2. 3 cm−1 at TC - 1K = 126 K; in the paraelectric D16 2h phase the soft TO has B2u symmetry varies from 11. 2 cm−1 at 167 K to 3. 2 cm−1 at TC + 3 K = 130 K. A Curie constant of 25 ± 2 K is deduced, which differs from that of 57 K measured in the MHz regime, indicating significant dispersion. This ferroelectric is unique in that the A1(LO) and B2u(LO) modes also soften substantially; in the C2v phase A1(LO) varies from 31 cm−1 at 4 K to 4 cm−1 at TC - 1K. This shows that ferroelectricity in TSCC does not arise from a subtle cancellation of short-range and long-range forces, as in Cochran's theory, but from an intrinsic instability in the short-range force associated with the N-H-Cl hydrogen bonds.

Soft-mode spectroscopy of tris-sarcosine calcium chloride

We have measured soft modes associated with the second-order ferroelectric phase transition in tris-sarcosine calcium chloride, (CH3NHCH2COOH)3 CaCL2, in both paraelectric D2h16 (Pnma) phase, and ferroelectric C2v9 phase. In the paraelectric phase the mode decreases from 11.2 cm-1 at 167K to 3.2 cm-1 at 130 K (TC = 127 K) and is underdamped over most of this range. A Curie constant of 25 ± 2 K is deduced from these infrared data, in fair agreement with that of 58 K measured in the megahertz regime via conventional dielectric studies. In the ferroelectric phase the mode is measured from 30.5 cm-1 at 4 K to 2.3 cm-1 at 126 K. The system is unique inasmuch as the longitudinal optical phonon decreases in energy by 90% between T = 0 and T = TC, in contrast to normal ferroelectrics in which LO energy is nearly independent of temperature; this shows that the inherent instability in the lattice is in the short-range forces and not to any subtle cancellation of short-range and long-range forces, as proposed in Coc...

Millimeter-wavelength spectroscopy of the ferroelectric phase transition in tris-sarcosine calcium chloride [(CH3NHCH2COOH)3CaCl2

Soft modes associated with the second-order ferroelectric phase transition in tris-sarcosine calcium chloride (TSCC) have been measured by use of a backward-wave oscillator in the region 2-30 ${\mathrm{cm}}^{\ensuremath{-}1}$. A resonant mode is found in both ferroelectric and paraelectric phases. In the paraelectric ${D}_{2h}^{16} (\mathrm{Pnma})$ phase the mode decreases from 11.2 ${\mathrm{cm}}^{\ensuremath{-}1}$ at 167 K to 3.2 ${\mathrm{cm}}^{\ensuremath{-}1}$ at 130 K and yields a Curie constant of 25\ifmmode\pm\else\textpm\fi{}2 K, in reasonable agreement with low-frequency dielectric measurements. In the ferroelectric phase the mode is underdamped at most temperatures and could be measured down to 2.3 ${\mathrm{cm}}^{\ensuremath{-}1}$, at which energy it is still a resonant although overdamped excitation. These new data show that TSCC is a proper, displacive ferroelectric, with a single phase transition, contrary to earlier suggestions.

VO Epr studies on lattice strains and the ferroelectric phase transition in tris-sarcosine calcium chloride crystals

The molecular origin for the spontaneous strains and the ferroelectric phase transition in tris-sarcosine calcium chloride (TSCC) crystals was investigated by means of VO++ EPR probes. VO++ impurities substituted for Ca++ ions in the TSCC lattice exhibited six spectra, corresponding to the interaction with individual ligand sarcosine molecules. We have considered that the pseudo-trigonal lattice symmetry is represented by the asymmetrical Ca++-sarcosine complex, which was found to approach a symmetrical octahedron with increasing temperature.At high temperatures, the impurity ion acquires another stable direction under a low strain condition, reorienting its axis between this and the original directions. While VO++ ions at Ca++ sites are perturbed by the sarcosine mode, this new direction is characterized by the absence of local strains, thereby the nature of lattice strains can be deduced from annealed TSCC crystals.In the ferroelectric phase, the VO++ lines are displaced by the internal electric field due to the spontaneous polarization, suggesting that a u-mode composed of the sarcosine cluster is frozen, shifting the dipolar directions toward the ferroelectric b-axis.

Logarithmic correction of the electric susceptibility in paraelectric tris-sarcosine calcium chloride

The dielectric constant tris-sarcosine calcium chloride [${(\mathrm{C}{\mathrm{H}}_{3}\ensuremath{-}\mathrm{N}\mathrm{H}\ensuremath{-}\mathrm{C}{\mathrm{H}}_{2}\ensuremath{-}\mathrm{C}\mathrm{O}\mathrm{O}\mathrm{H})}_{3}$\ifmmode\cdot\else\textperiodcentered\fi{}Ca${\mathrm{Cl}}_{2}$] has been measured with a relative precision of \ensuremath{\sim}0.0005 from the transition temperature ${T}_{c}$ to ${T}_{c}+60$ K. Over more than 2 orders of magnitude of reduced temperature [$\frac{(T\ensuremath{-}{T}_{c})}{{T}_{c}}$], it follows accurately the logarithmically corrected mean-field behavior of uniaxial dipolar ferroelectrics. It is shown unambiguously that these corrections are superior to a power law. Close to ${T}_{c}$ ($T&lt;{T}_{c}+0.3$ K), the dielectric constant becomes affected by roundoff effects. Previous results on tris-sarcosine calcium chloride are reviewed in the light of these new findings.

Electron nuclear double resonance of 13C nuclei with natural abundance in trissarcosine calcium chloride doped with Mn 2+ ions

13C ENDOR measurements were performed at 4.2 K on single crystals of trissarcosine calcium chloride doped with Mn 2+ ions. Hyperfine coupling tensors were measured for six 13C nuclei of the carboxyl groups. An attempt is made to interpret the data in terms of electron-transfer and dipole—dipole contributions.

13C NMR investigations of the ferroelectric phase transition of tris-sarcosine calcium chloride

13C NMR spectra were measured for tris-sarcosine calcium chloride (TSCC) crystals in the paraelectric phase (at temperatures of ⋍ 300 and 150 K) and in the ferroelectric phase (at temperatures of 119 K) by double-resonance techniques with proton decoupling. The ferroelastic single crystals were rotated around their three crystallographic axes to derive the tensors of magnetic shielding for the different carboxylic carbon atoms. There is no change of the eigenvalues and eigenvectors of the tensors at the phase transition. The results are consistent with the interpretation of former EPR data.

Temperature and pressure dependence of dielectric properties of deuterated trissarcosine calcium chloride

The dielectric properties (permittivity, dielectric loss tangent, spontaneous polarisation, coercive field and phase transition temperatures) of deuterated trissarcosine calcium chloride (DTSCC) are presented in the temperature range -200 to -60 degrees C and in the pressure range up to 7 kbar. An abrupt decrease in the permittivity occurs at a pressure of about 5 kbar, and the probably antiferroelectric phase is induced by the application of pressure. The pressure-temperature phase diagram of DTSCC is similar to that of TSCC. The ferroelectric transition temperature of DTSCC(Tcd) is found to be nearly equal to that of TSCC (Tc), contrary to the isotope shift of the ferroelectric transition temperature from Tc=-146 to Tcd=-124 degrees C reported previously.

The concentration dependence of the ferroelectric transition temperature of the solid solution of TSCC and TSCB

The concentration dependence of the ferroelectric transition temperature T c of single crystals of the solid solution tris-sarcosine calcium chloride 1− x bromide x is studied experimentally by measurement of the static dielectric constant ϵ b and described by the empirical relation T c(X) = T c(0) [1−(X/X c)] 1 2 . The Ising model with transverse field and the model of coupled anharmonic oscillators are used to explain the concentration dependence of the transition temperature T c .