Dipole Glass Phase in an Isolated Hydrogen-Bonded Mixed Crystal [(NH$_4$)$_{1-x}$Rb$_x$]$_3$H(SO$_4$)$_2$ ($x$ = 0.58)

[(NH$_4$)$_{1-x}$Rb$_x$]$_3$H(SO$_4$)$_2$ mixed crystals were investigated by dielectric constant measurement and Raman spectroscopy from room temperature to 7 K. In contrast to the result of (NH$_4$)$_3$H(SO$_4$)$_2$ ($x=0$) showing multiple phase transitions, [(NH$_4$)$_{1-x}$Rb$_x$]$_3$H(SO$_4$)$_2$ ($x=0.58$) mixed crystal does not show any remarkable dielectric anomaly but a weak dielectric dispersion below 40 K, which is characterized by the Arrhenius law. From the measurement of the Raman spectra of both crystals, it is confirmed that the [(NH$_4$)$_{1-x}$Rb$_x$]$_3$H(SO$_4$)$_2$ ($x=0.58$) mixed crystal shows a global symmetry conservation between the two spectra measured at room temperature and at 20 K while the (NH$_4$)$_3$H(SO$_4$)$_2$ crystal exhibits drastic structural changes associated with the sequence of the phase transitions. It is concluded that [(NH$_4$)$_{1-x}$Rb$_x$]$_3$H(SO$_4$)$_2$ ($x=0.58$) mixed crystal shows a new dipole glass phase in the isolated hydrogen-bonded system. KCI Citation Count: 0