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Persistent URL http://purl.org/net/epubs/work/48580700
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Record Id 48580700
Title Structural phase transitions in the geometric ferroelectric LaTaO4
Abstract The recent report of an intermediate incommensurately modulated orthorhombic phase in LaTaO4 has prompted a re-examination of the phase transition sequence in LaTaO4 as a function of temperature. With falling temperature, the sequence of phases examined is (orthorhombic) Cmc21(C)↔Cmc21(IC)↔(monoclinic)P21/c, with C and IC denoting commensurate and incommensurate phases, respectively. The orthorhombic to monoclinic transition, Tm−o, is a first order reconstructive transition occurring at 440 K and TIC−C is a first-order displacive transition occurring at 500–530 K. Strain and elasticity data confirm a first-order transition between the basic and modulated Cmc21 phases, with similarities to the isostructural fluoride BaMnF4. A Raman spectroscopic study of the LaTaO4 phase transition indicates that the IC-C phase transition is driven by a soft zone-boundary phonon (unstable) of the commensurate orthorhombic (Cmc21) phase. The soft phonon is found to appear (underdamped) above 443 K and vanishes (overdamped) around 528 K. A large supercell of the monoclinic phase below Tm−o is proposed based on the Raman spectroscopic results.
Organisation ISIS , ISIS-HRPD , STFC
Funding Information EPSRC (EP/N509759/1); EPSRC (EP/P024637/1); EPSRC (EP/P024904/1); EPSRC (EP/I036079/1); DOD (FA9550-20-1-0064); NERC (NE/B505738/1); NERC (NE/F017081/1)
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Language English (EN)
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Journal Article Phys Rev B 103, no. 1 (2021): 014119. doi:10.1103/PhysRevB.103.014119 2021