High-Pressure Synthesis and Magnetism of the 4 H-BaMnO3 Single Crystal and Its 6 H-Type Polymorph

Shijun Qin; Yi-Ying Chin; Bowen Zhou; Zhehong Liu; Xubin Ye; Jia Guo; Guangxiu Liu; Chien-Te Chen; Zhiwei Hu; Youwen Long

doi:10.1021/acs.inorgchem.1c02155

High-Pressure Synthesis and Magnetism of the 4 H-BaMnO₃ Single Crystal and Its 6 H-Type Polymorph

Inorg Chem. 2021 Nov 1;60(21):16308-16315. doi: 10.1021/acs.inorgchem.1c02155. Epub 2021 Oct 18.

Authors

Shijun Qin^{1

2}, Yi-Ying Chin³, Bowen Zhou^{1

2}, Zhehong Liu^{1

2}, Xubin Ye^{1

2}, Jia Guo^{1

2}, Guangxiu Liu^{1

2}, Chien-Te Chen⁴, Zhiwei Hu⁵, Youwen Long^{1

2

6}

Affiliations

¹ Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
² School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China.
³ Department of Physics, National Chung Cheng University, Chiayi 62102, Taiwan.
⁴ National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan.
⁵ Max Planck Institute for Chemical Physics of Solids, Dresden 01187, Germany.
⁶ Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, China.

PMID: 34658238
DOI: 10.1021/acs.inorgchem.1c02155

Abstract

A 4H-type BaMnO₃ single crystal was prepared by combining the floating zone method with high-pressure treatment at 5 GPa and 1023 K. The crystal crystallizes to a hexagonal structure with space group P6₃/mmc and lattice parameters a = 5.63723(5) Å and c = 9.22355(8) Å. In this structure, face-sharing MnO₆ octahedral dimers connect with each other by corner O atoms along the c-axis direction, forming an -A-B-A-C-type 4H arrangement. A long-range antiferromagnetic (AFM) phase transition is found to occur at T_N ≈ 263 K. When the synthesis pressure increases to 20 GPa, a new polymorphic phase is obtained. This higher-pressure phase still possesses the hexagonal P6₃/mmc symmetry, but the lattice parameters change to be a = 5.61349(2) Å and c = 13.66690(9) Å with a unit cell volume reduction of 2.05%. In this new phase, the c-axis MnO₆ dimers are separated by MnO₆ octahedral layers in the ab plane, forming an -A-B-C-A-C-B-type 6H structure. The 6H phase exhibits two long-range AFM orderings at T_N1 ≈ 220 K and T_N2 ≈ 25 K, respectively. The different magnetic properties are discussed on the basis of the detailed structural constitutions of 4H- and 6H-BaMnO₃.