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We report detailed dielectric investigations of Pr 1− x Ca x MnO 3 (PCMO, x =0.5) ceramics, a member of the perovskite manganite family that exhibits a colossal magnetoresistance. Analysis of the electrical conductivity and dielectric constant data revealed that in the low temperature phase, below 42 K, small polarons are responsible for the charge transport in the system. This provides a new understanding of the phase diagrams in PCMO systems

Orthorhombic CsH 2 PO 4 undergoes a ferroelectric transition at T c = −119.5° C , whereas the ferroelectric transition temperature in isomorphous CsD 2 PO 4 is T c = −5.55° C . The transitions are of first order in both cases. The rather large isotope effect demonstrates the importance of the OHO bonds in the transition mechanism.

The temperature dependence of the static dielectric constant, the spontaneous polarization and the electric field dependence of the polarization in TSCC have been measured. The critical exponents γ, β and δ were determined. The values obtained are consistent with the predictions of the mean field theory, and β in particular seems to be different from the one determined with EPR techniques.

The observation of a thermal hysteresis indicates that the phase transitions in KDA, KD†A, RDA and CDA crystals are of the first order. The static dielectric properties of these ferroelectrics resemble those of KD†P.

The dependence of the spontaneous polarization on temperature and electric field has been measured for ferroelectric triglycine sulphate (TGS) and deuterated triglycine sulphate (D-TGS), and the critical exponents γ3, γ4, γ7, γ9, and γ10 have been determined. The results are consistent with the predictions of the mean field theory for ϵ = (T c − T) T c ⩾ 1.2.10 −4 and E > 30 V/cm. For lower values of either ϵ or E systematic deviations seem to occur and the values of the exponents seem to deviate from the mean field theory and approach those predicted by the 3-dimensional Ising model.

The dependence of the proton T1, T1ϱ and the dipolar splitting of the proton resonance line δ on the angle between the nematic director and the magnetic field was measured in a nematic 67 mol.% MBBA and 33 mol.% EBBA mixture by exploiting the fact that the magnetic field orientation time is much longer than the proton T1. The results show that — as in pure MBBA — translational diffusion rather than order director fluctuations (ODF) represent the dominant relaxation mechanism for T−11 in this system whereas there is a 30% ODF contribution to T−11ϱ. It is further shown that the T1∝“ω 1 2 L” ODF dispersion law does not hold at arbitrarily low Larmor frequencies and that (T1)ODF approaches a constant value as ωL→0.

The dielectric constant of deuterated ammonium Rochelle salt along the three crystallographic axes as well as the pyroelectric charge density developed on the crystal surface perpendicularly to the b-axis have been measured with a high temperature resolution. The para- to ferroelectric transition at Tc = −159°C shows a thermal hysteresis of ΔT = 0.15°C. This and the discontinuities in the dielectric constant along all three axes show that the phase transition is of the first-order. No phase intermediate between the para- and the ferroelectric phases could be detected.