中国物理B ›› 2020, Vol. 29 ›› Issue (8): 86501-086501.doi: 10.1088/1674-1056/ab8a36

• SPECIAL TOPIC—Ultracold atom and its application in precision measurement • 上一篇    下一篇

Negative thermal expansion of Ca2RuO4 with oxygen vacancies

Sen Xu(徐森), Yangming Hu(胡杨明), Yuan Liang(梁源), Chenfei Shi(史晨飞), Yuling Su(苏玉玲), Juan Guo(郭娟), Qilong Gao(高其龙), Mingju Chao(晁明举), Erjun Liang(梁二军)   

  1. 1 Key Laboratory of Materials Physics of Education of China, School of Physics and Microelectronics, Zhengzhou University, Zhengzhou 450001, China;
    2 Department of Applied Physics, Donghua University, Shanghai 201620, China;
    3 School of Physics and Electronic Engineering, Zhengzhou University of Light Industry, Zhengzhou 450001, China
  • 收稿日期:2020-03-19 修回日期:2020-04-10 出版日期:2020-08-05 发布日期:2020-08-05
  • 通讯作者: Yuan Liang, Erjun Liang E-mail:yliang@dhu.edu.cn;ejliang@zzu.edu.cn
  • 基金资助:
    Project supported by the National Natural Science Foundation of China (Grant Nos. 11874328 and 11574276). The SXRD experiments were performed at the BL02B2 and BL04B2 of SPring-8 with the approval of the Japan Synchrotron Radiation Research Institute (JASRI; proposal Nos. 2019A1167, 2019A1095, and 2019A1340). We also acknowledge the help of Beamline Scientists Dr. Lirong Zheng (BSRF), Dr. Shogo Kawaguchi, and Dr. Koji Ohara (SPring-8).

Negative thermal expansion of Ca2RuO4 with oxygen vacancies

Sen Xu(徐森)1, Yangming Hu(胡杨明)1, Yuan Liang(梁源)2, Chenfei Shi(史晨飞)3, Yuling Su(苏玉玲)3, Juan Guo(郭娟)1, Qilong Gao(高其龙)1, Mingju Chao(晁明举)1, Erjun Liang(梁二军)1   

  1. 1 Key Laboratory of Materials Physics of Education of China, School of Physics and Microelectronics, Zhengzhou University, Zhengzhou 450001, China;
    2 Department of Applied Physics, Donghua University, Shanghai 201620, China;
    3 School of Physics and Electronic Engineering, Zhengzhou University of Light Industry, Zhengzhou 450001, China
  • Received:2020-03-19 Revised:2020-04-10 Online:2020-08-05 Published:2020-08-05
  • Contact: Yuan Liang, Erjun Liang E-mail:yliang@dhu.edu.cn;ejliang@zzu.edu.cn
  • Supported by:
    Project supported by the National Natural Science Foundation of China (Grant Nos. 11874328 and 11574276). The SXRD experiments were performed at the BL02B2 and BL04B2 of SPring-8 with the approval of the Japan Synchrotron Radiation Research Institute (JASRI; proposal Nos. 2019A1167, 2019A1095, and 2019A1340). We also acknowledge the help of Beamline Scientists Dr. Lirong Zheng (BSRF), Dr. Shogo Kawaguchi, and Dr. Koji Ohara (SPring-8).

摘要: Oxygen vacancies have a profound effect on the magnetic, electronic, and transport properties of transition metal oxides but little is known about their effect on thermal expansion. Herein we report the effect of oxygen defects on the structure formation and thermal expansion properties of the layered perovskite Ca2RuO4 (CRO). It is shown that the CRO containing excess oxygen crystallizes in a metallic L-CRO phase without structure transition from 100 K to 500 K and displays a normal thermal expansion behavior, whereas those with oxygen vacancies adopt at room temperature an insulating S-CRO phase and exhibit an enormous negative thermal expansion (NTE) from 100 K to about 360 K, from where they undergo a structure transition to a high temperature metallic L-CRO phase. Compared to the L-CRO containing excess oxygen, the S-CRO structure has increasingly large orthorhombic strain and distinctive in-plane distortion upon cooling. The in-plane distortion of the RuO6 octahedra reaches a maximum across 260 K and then relaxes monotonically, providing a structure evidence for the appearance of an antiferromagnetic orbital ordering in the paramagnetic phase and the A_g phonon mode suppression and phase flip across the same temperature found recently. Both the L-and S-CRO display an antiferromagnetic ordering at about 150-110 K, with ferromagnetic ordering components at lower temperature. The NTE in S-CRO is a result of a complex interplay among the spin, orbital, and lattice.

关键词: negative thermal expansion, structure, oxygen vacancies, metal-insulator transition, octahedra distortion

Abstract: Oxygen vacancies have a profound effect on the magnetic, electronic, and transport properties of transition metal oxides but little is known about their effect on thermal expansion. Herein we report the effect of oxygen defects on the structure formation and thermal expansion properties of the layered perovskite Ca2RuO4 (CRO). It is shown that the CRO containing excess oxygen crystallizes in a metallic L-CRO phase without structure transition from 100 K to 500 K and displays a normal thermal expansion behavior, whereas those with oxygen vacancies adopt at room temperature an insulating S-CRO phase and exhibit an enormous negative thermal expansion (NTE) from 100 K to about 360 K, from where they undergo a structure transition to a high temperature metallic L-CRO phase. Compared to the L-CRO containing excess oxygen, the S-CRO structure has increasingly large orthorhombic strain and distinctive in-plane distortion upon cooling. The in-plane distortion of the RuO6 octahedra reaches a maximum across 260 K and then relaxes monotonically, providing a structure evidence for the appearance of an antiferromagnetic orbital ordering in the paramagnetic phase and the A_g phonon mode suppression and phase flip across the same temperature found recently. Both the L-and S-CRO display an antiferromagnetic ordering at about 150-110 K, with ferromagnetic ordering components at lower temperature. The NTE in S-CRO is a result of a complex interplay among the spin, orbital, and lattice.

Key words: negative thermal expansion, structure, oxygen vacancies, metal-insulator transition, octahedra distortion

中图分类号:  (Thermal expansion; thermomechanical effects)

  • 65.40.De
61.66.-f (Structure of specific crystalline solids) 71.30.+h (Metal-insulator transitions and other electronic transitions) 61.72.jd (Vacancies)