Observation of the freezing line in a deuteron glass

Abstract

The phase diagram of the deuteron glass Rbq (ND4), DsPO4 has been determined experimentally in the entire range of concentration z. A recently introduced temperature-frequency plot has been used to analyze the shape of the dielectric relaxation spectrum, indicating that in the glassy regime the longest relaxation time diverges according to the Vogel-Fulcher law. The corresponding Vogel-Fulcher temperature has been identified as the static limit of the freezing temperature Ty. The phase boundaries of the ferroelectric and antiferroelectric phases have been obtained in a standard manner by observing the peaks and breaks, respectively, in the temperature dependence of the quasistatic dielectric constant. It is shown that in a broad concentration range the observed phase diagram can be quantitatively described by a mean-field theory based on the static random-bond random-field model of dipolar glasses. The absence of macroscopic polarization in the ferroelectric region close to the glassy phase is probably due to the formation of microdomains in the presence of local random fields, however, recent NMR data suggest that a phase segregation between ferroelectric and glassy regions may occur.

Thermodynamics, dielectric permittivity and phase diagrams of the Rb_{1-x}(NH_{4})_{x}H_{2}PO_{4} type proton glasses

“…As a result, we obtain the same expression forη µ , except that for the eigenvaluesF [12] µ we have to use the linear combination like forφ µ .…”

“…The temperatures T g (x), corresponding to the maximum of ε 11 (T, ν) (inflection point of [12] at ν=1 kHz and T g =53 K [9] at ν=10 kHz, and both in [12] and [9] T g (x) increases with frequency.…”

“…The following regions are present in these diagrams: HP (high-temperature region of paraelectric phase), LP (low-temperature region of paraelectric phase), F ( ferroelectric phase), AF (antiferroelectric phase) (figures 11, 12). - [12], - [13], - [49]. The solid lines are the Tc, TN, and Tg transitions obtained from the maxima of ε33(T ) and ε11(T ).…”

“…Experimental measurements of the dielectric permittivity of Rb 1−x (NH 4 ) x H 2 PO 4 [1][2][3][4][5][6][7][8], Rb 1−x (ND 4 ) x D 2 PO 4 [7,[9][10][11][12][13][14], Rb 1−x (NH 4 ) x H 2 AsO 4 [15][16][17][18], and K 1−x (NH 4 ) x H 2 PO 4 [19][20][21][22][23] in the glass phase composition region have shown that the temperature curves of the longitudinal ε 33 (T, ν) and transverse ε 11 (T, ν) permittivities are qualitatively similar. At high temperatures the real parts of the permittivities are roughly described by the Curie-Weiss law.…”

“…Symmetry of the matrix F [21] c is the same as ofq ; after the unitary transformation it becomes analogous to the antidiagonal matrixq with the corresponding elementsF [21] µ . The matrix F [12] c is transposed to F [21] c . After the unitary transformation and exclusion of the parametersφ µ ,q µ we obtain expressions for the correlators η µ , entering the expression for the system susceptibility.…”