Critical exponents of ferroelectric transitions in modulated SrTiO3：Consequences of quantum fluctuations and quenched disorder

doi:10.1088/1674-1056/22/7/077701

中国物理B ›› 2013, Vol. 22 ›› Issue (7): 77701-077701.doi: 10.1088/1674-1056/22/7/077701

• CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES • 上一篇下一篇

Critical exponents of ferroelectric transitions in modulated SrTiO₃：Consequences of quantum fluctuations and quenched disorder

王景雪, 刘美风, 颜志波, 刘俊明

Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093, China

收稿日期:2013-02-18 修回日期:2013-03-14 出版日期:2013-06-01 发布日期:2013-06-01
基金资助:
Project supported by the National Basic Research Program of China (Grant Nos. 2011CB922101 and 2009CB623303), the National Natural Science Foundation of China (Grant Nos. 11234005 and 11074113), and the Priority Academic Development Program of Jiangsu Higher Education Institutions, China.

Critical exponents of ferroelectric transitions in modulated SrTiO₃：Consequences of quantum fluctuations and quenched disorder

Wang Jing-Xue (王景雪), Liu Mei-Feng (刘美风), Yan Zhi-Bo (颜志波), Liu Jun-Ming (刘俊明)

Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093, China

Received:2013-02-18 Revised:2013-03-14 Online:2013-06-01 Published:2013-06-01
Contact: Liu Jun-Ming E-mail:liujm@nju.edu.cn
Supported by:
Project supported by the National Basic Research Program of China (Grant Nos. 2011CB922101 and 2009CB623303), the National Natural Science Foundation of China (Grant Nos. 11234005 and 11074113), and the Priority Academic Development Program of Jiangsu Higher Education Institutions, China.

摘要/Abstract

摘要： The ferroelectric transitions of several SrTiO₃-based ferroelectrics are investigated experimentally and theoretically, with special attention to the critical scaling exponents associated with the phase transitions, in order to understand the competition among quantum fluctuations (QFs), quenched disorder, and ferroelectric ordering. Two representative systems with sufficiently strong QFs and quenched disorders in competition with the ferroelectric ordering are investigated. We start from non-stoichiometric SrTiO₃ (STO) with the Sr/Ti ratio deviating slightly from one, which is believed to maintain strong QFs. Then, we address Ba/Ca co-doped Sr_1-x(Ca_0.6389Ba_0.3611)_xTiO₃ (SCBT) with the averaged Sr-site ionic radius identical to the Sr²⁺ ionic radius, which is believed to offer remarkable quenched disorder associated with the Sr-site ionic mismatch. The critical exponents associated with polarization P and dielectric susceptibility ε, respectively, as functions of temperature T close to the critical point T_c, are evaluated. It is revealed that both non-stoichiometric SrTiO₃ and SCBT exhibit much bigger critical exponents than the Landau mean-field theory predictions. These critical exponents then decrease gradually with increasing doping level or deviation of Sr/Ti ratio from one. A transverse Ising model applicable to the Sr-site doped STO (e.g., Sr_1-xCa_xTiO₃) at low level is used to explain the observed experimental data. It is suggested that the serious deviation of these critical exponents from the Landau theory predictions in these STO-based systems is ascribed to the significant QFs and quenched disorder by partially suppressing the long-range spatial correlation of electric dipoles around the transitions. The present work thus sheds light on our understanding of the critical behaviors of ferroelectric transitions in STO in the presence of quantum fluctuations and quenched disorder, whose effects have been demonstrated to be remarkable.

关键词: critical exponents, quantum fluctuations, ferroelectric phase transitions

Abstract: The ferroelectric transitions of several SrTiO₃-based ferroelectrics are investigated experimentally and theoretically, with special attention to the critical scaling exponents associated with the phase transitions, in order to understand the competition among quantum fluctuations (QFs), quenched disorder, and ferroelectric ordering. Two representative systems with sufficiently strong QFs and quenched disorders in competition with the ferroelectric ordering are investigated. We start from non-stoichiometric SrTiO₃ (STO) with the Sr/Ti ratio deviating slightly from one, which is believed to maintain strong QFs. Then, we address Ba/Ca co-doped Sr_1-x(Ca_0.6389Ba_0.3611)_xTiO₃ (SCBT) with the averaged Sr-site ionic radius identical to the Sr²⁺ ionic radius, which is believed to offer remarkable quenched disorder associated with the Sr-site ionic mismatch. The critical exponents associated with polarization P and dielectric susceptibility ε, respectively, as functions of temperature T close to the critical point T_c, are evaluated. It is revealed that both non-stoichiometric SrTiO₃ and SCBT exhibit much bigger critical exponents than the Landau mean-field theory predictions. These critical exponents then decrease gradually with increasing doping level or deviation of Sr/Ti ratio from one. A transverse Ising model applicable to the Sr-site doped STO (e.g., Sr_1-xCa_xTiO₃) at low level is used to explain the observed experimental data. It is suggested that the serious deviation of these critical exponents from the Landau theory predictions in these STO-based systems is ascribed to the significant QFs and quenched disorder by partially suppressing the long-range spatial correlation of electric dipoles around the transitions. The present work thus sheds light on our understanding of the critical behaviors of ferroelectric transitions in STO in the presence of quantum fluctuations and quenched disorder, whose effects have been demonstrated to be remarkable.

Key words: critical exponents, quantum fluctuations, ferroelectric phase transitions

中图分类号: (Dielectric properties of solids and liquids)

77.22.-d

77.80.B- (Phase transitions and Curie point) 71.55.Jv (Disordered structures; amorphous and glassy solids)

王景雪, 刘美风, 颜志波, 刘俊明. Critical exponents of ferroelectric transitions in modulated SrTiO₃：Consequences of quantum fluctuations and quenched disorder[J]. 中国物理B, 2013, 22(7): 77701-077701.

Wang Jing-Xue (王景雪), Liu Mei-Feng (刘美风), Yan Zhi-Bo (颜志波), Liu Jun-Ming (刘俊明). Critical exponents of ferroelectric transitions in modulated SrTiO₃：Consequences of quantum fluctuations and quenched disorder[J]. Chin. Phys. B, 2013, 22(7): 77701-077701.

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Critical exponents of ferroelectric transitions in modulated SrTiO₃：Consequences of quantum fluctuations and quenched disorder

Critical exponents of ferroelectric transitions in modulated SrTiO₃：Consequences of quantum fluctuations and quenched disorder

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