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Quasiharmonic model for ferroelectric transition in ^<18>O-isotope exchanged SrTiO_3

Journal of physics. Condensed matter Volume 20 Issue 5
published_at 2008-01
2007020131.pdf
[fulltext] 515 KB
Title
Quasiharmonic model for ferroelectric transition in ^<18>O-isotope exchanged SrTiO_3
Creators Mashiyama Hiroyuki
Creators Mashiyama H.
By extending the quasiharmonic approximation to a quantum particle within a local potential of the double Morse type, a model describing the ferroelectric phase transition in SrTiO_3 induced by oxygen isotope replacement is developed. The theory uses the variational principle method at finite temperature with emphasis on the quantum effect manifested in zero-point vibration. The ferroelectric-paraelectric transition in SrTi(^<16>O_<1-x> ^18O_x)_3 is analyzed and the x-T_c phase diagram is compared with the experimental one in order to confirm the qualitative validity of the model. The quantum mechanical effect and the evolution of the ferroelectricity in SrTi(^<16>O_<1-x> ^18O_x)_3 are also demonstrated theoretically and the soft mode of SrTi(^<16>O_<1-x> ^18O_x)_3 shows a perfect softening at the ferroelectric phase transition for x≧x_c≒0.32. Finally, the study shows the importance of the mass of component ions and that isotope introduction has several effects even if the mass effect is predominant.
Languages eng
Resource Type journal article
Publishers Institute of Physics
Date Issued 2008-01
File Version Author’s Original
Access Rights open access
Relations
[ISSN]0953-8984
[NCID]AA10672168
https://doi.org/10.1088/0953-8984/20/5/055223
[isVersionOf] [URI]http://www.iop.org/EJ/journal/JPhysCM
Schools 大学院理工学研究科(理学)