Deuteron NMR study of dynamics and of coexistence of paraelectric and ferroelectric phases in Rb0.90(ND4)0.10D2AsO4
Pinto, Nicholas J.
Howell, Francis L.
Schmidt, V. Hugo
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The deuteron glass Rb1−x(ND4)xD2AsO4 (DRADA) is a mixed crystal of RbD2AsO4 (DRDA) and ND4D2AsO4 (DADA). Deuteron nuclear magnetic resonance has been performed on the acid and ammonium deuterons. The crystal studied has an ammonium concentration (x=0.10) that puts it in the coexistence region of the phase diagram. Line-shape measurements of the ammonium deuterons show the coexistence of the ferroelectric (FE) and paraelectric (PE) phases as the temperature is lowered below the ferroelectric-phase-transition temperature Tc. The acid deuteron line shape on the other hand is found to broaden as the temperature is reduced but is unaffected by the ferroelectric transition. Spin-lattice-relaxation measurements have been performed and the activation energies for the relaxation processes have been computed. The relaxation-rate anomaly for acid deuterons in the ferroelectric-transition range indicates a short correlation length for the FE phase in the coexistence region of the phase diagram.
N.J. Pinto, F.L. Howell, and V.H. Schmidt, “Deuteron NMR study of dynamics and of coexistence of paraelectric and ferroelectric phases in Rb0.90(ND4)0.10D2AsO4,” Phys. Rev. B 48, 5983-5896 (1993).