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Temperature and concentration dependences of Raman vibrational modes in Rb{sub 1{minus}x}(ND{sub 4}){sub x}D{sub 2}AsO{sub 4} mixed crystals

Journal Article · · Physical Review, B: Condensed Matter
;  [1];  [2]
  1. Department of Physics, Fu-Jen University, Taipei, Taiwan, Republic of (China)
  2. Department of Physics, Montana State University, Bozeman, Montana 59717 (United States)
The Raman vibrations (10{endash}10{sup 3} cm{sup {minus}1}) of A{sub 1}, B{sub 2}, and E symmetries along the [110] phonon direction have been measured as a function of temperature (80{endash}293 K) in the mixed ferroelectric (FE) antiferroelectric system Rb{sub 1{minus}x}(ND{sub 4}){sub x}D{sub 2}AsO{sub 4} (DRADA-x) for ammonium concentrations x=0, 0.10, and 0.28. With decreasing temperature, the B{sub 2} Raman shifts of RbD{sub 2}AsO{sub 4} show both softening and hardening anomalies for four selected modes. In DRADA-0.10, the bending mode {nu}{sub 2}(B{sub 2}) (near 280 cm{sup {minus}1}) of the AsO{sub 4} group exhibits a gradual softening down to T{approximately}125 K and then has a rapid drop. This phenomenon is attributed to a quick development of long-range FE ordering. In DRADA-0.28, the in-plane bending mode {delta}(O-D) (B{sub 2}) shows a softening near 220 K, whereas the bending mode {nu}{sub 2}(B{sub 2}) of the AsO{sub 4} group exhibits a hardening. We associate these anomalies with the onset of glass formation. A doublet with splitting of about 10 cm{sup {minus}1} was observed in the {nu}{sub 1} modes and was attributed to a slight deformation of the {nu}{sub 1} vibration due to AsO{sub 4} groups having different nearby ions (ND{sub 4} and Rb). {copyright} {ital 1997} {ital The American Physical Society}
DOE Contract Number:
FG05-91ER79046
OSTI ID:
450365
Journal Information:
Physical Review, B: Condensed Matter, Journal Name: Physical Review, B: Condensed Matter Journal Issue: 5 Vol. 55; ISSN PRBMDO; ISSN 0163-1829
Country of Publication:
United States
Language:
English