Structural phase transitions in the geometric ferroelectric LaTa O4

Grant W. Howieson; Karuna K. Mishra; Alexandra S. Gibbs; Ram S. Katiyar; James F. Scott; Finlay D. Morrison; Michael Carpenter

doi:10.1103/PhysRevB.103.014119

Structural phase transitions in the geometric ferroelectric LaTa O₄

Grant W. Howieson, Karuna K. Mishra, Alexandra S. Gibbs, Ram S. Katiyar, James F. Scott, Finlay D. Morrison^*, Michael Carpenter^*

^*Corresponding author for this work

Research output: Contribution to journal › Article › peer-review

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, T_m-o, is a first order reconstructive transition occurring at 440 K and T_IC-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 T_m-o is proposed based on the Raman spectroscopic results.

Original language	English
Article number	014119
Number of pages	12
Journal	Physical Review. B, Condensed matter and materials physics
Volume	103
Issue number	1
DOIs	https://doi.org/10.1103/PhysRevB.103.014119
Publication status	Published - 29 Jan 2021

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10.1103/PhysRevB.103.014119

Howieson-2021-Structural-phase-PhysRevB-103-014119
Copyright © 2021 American Physical Society. This work has been made available online in accordance with publisher policies or with permission. Permission for further reuse of this content should be sought from the publisher or the rights holder. This is the final published version of the work, which was originally published at https://doi.org/10.1103/PhysRevB.103.014119.
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title = "Structural phase transitions in the geometric ferroelectric LaTa O4",

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.",

author = "Howieson, \{Grant W.\} and Mishra, \{Karuna K.\} and Gibbs, \{Alexandra S.\} and Katiyar, \{Ram S.\} and Scott, \{James F.\} and Morrison, \{Finlay D.\} and Michael Carpenter",

note = "Funding: School of Chemistry, University of St Andrews for funding of a studentship to GWH through the EPSRC doctoral training grant (Grant No. EP/N509759/1). This work was also facilitated by funding provided by the EPSRC (Grant No. EP/P024637/1). K.K.M. and R.S.K. acknowledge financial support from the Department of Defense, USA (DoD Grant No. FA9550-20-1-0064). The RUS component of this work was funded by EPSRC Grant No. EP/P024904/1.",

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AU - Howieson, Grant W.

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AU - Scott, James F.

AU - Morrison, Finlay D.

AU - Carpenter, Michael

N1 - Funding: School of Chemistry, University of St Andrews for funding of a studentship to GWH through the EPSRC doctoral training grant (Grant No. EP/N509759/1). This work was also facilitated by funding provided by the EPSRC (Grant No. EP/P024637/1). K.K.M. and R.S.K. acknowledge financial support from the Department of Defense, USA (DoD Grant No. FA9550-20-1-0064). The RUS component of this work was funded by EPSRC Grant No. EP/P024904/1.

PY - 2021/1/29

Y1 - 2021/1/29

N2 - 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.

AB - 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.

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VL - 103

JO - Physical Review. B, Condensed matter and materials physics

JF - Physical Review. B, Condensed matter and materials physics

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M1 - 014119

ER -

Structural phase transitions in the geometric ferroelectric LaTa O₄

Abstract

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New Horizon in Nanoscale: Ferrolectric, Ferroelastic and Multiferroic Domain Walls: a New Horizon in Nanoscale Functional Materials

Unidentified Phase Transition in Polar Lanthanum Tantalate (LaTaO4)

Incommensurate-commensurate transition in the geometric ferroelectric LaTaO₄

Synthesis and characterisation of the geometric ferroelectric LaTaO₄

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Structural phase transitions in the geometric ferroelectric LaTa O4

Abstract

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Other files and links

Fingerprint

Projects

New Horizon in Nanoscale: Ferrolectric, Ferroelastic and Multiferroic Domain Walls: a New Horizon in Nanoscale Functional Materials

Datasets

Unidentified Phase Transition in Polar Lanthanum Tantalate (LaTaO4)

Research output

Incommensurate-commensurate transition in the geometric ferroelectric LaTaO4

Student theses

Synthesis and characterisation of the geometric ferroelectric LaTaO₄

Cite this

Structural phase transitions in the geometric ferroelectric LaTa O₄

Incommensurate-commensurate transition in the geometric ferroelectric LaTaO₄