Linear and non-linear dielectric spectroscopy on ammonium doped Rochelle salt

In this work we present a thorough investigation of the mixed system of Roc helle salt doped with ammonium, with 0 less than or equal to x less than or equal to 1 for [Na(K1-x(NH4)(x))C4H4O6. 4H(2)O]. This interesting system i s known to exhibit a rich phase diagram with a variety of polar and non-pol ar phases. However, most of the earlier investigations date back many decad es and the experimental advances made since then should enable new insight into the physical nature of its phase diagram. We studied single crystals o f 18 doping concentrations using linear and non-linear frequency-dependent dielectric response spectroscopy. In the low field measurements a variety o f relaxation features are detected and analyzed in detail. The results for two concentrations of x = 0 and x = 0.15 are described qualitatively with a simple model. The most important outcome of the present work is the detect ion of a new electrically ordered phase for concentrations 0.18 < x < 0.89.