Coexistence of Proton-Glass and Ferroelectric Order in Rb1-x(NH4)xH2AsO4

Abstract

The mixed crystal Rb1−x(NH4)xH2AsO4 (RADA) has been investigated for several values of (x=0,0.12,0.15, and 0.20) by measuring the complex dielectric permittivity along the a tetragonal axis in the temperature range from 3 to 300 K and frequency range from 1 Hz to 30 kHz. We find coexistence of ferroelectric and proton-glass order in RADA for x=0.12 and probably at x=0.15. The long-range ferroelectric order is not destroyed by the onset of proton-glass ordering. This behavior is similar to that of other proton-glass systems and of the magnetic Ising glass systems reported by Wong et al. in Fe0.55Mg0.45Cl2 and by Yoshizawa et al. in FexMn1−xTiO3. The partial phase diagram for Rb1−x(NH4)xH2AsO4 including the coexisting proton-glass and ferroelectric phases is presented.