In-plane uniaxial pressure-induced out-of-plane antiferromagnetic moment and critical fluctuations in BaFe₂As

• Published in: Nature communications Vol. 11; no. 1
• Main Authors: Liu, Panpan, Klemm, Mason L., Tian, Long, Lu, Xingye, Song, Yu, Tam, David W., Schmalzl, Karin, Park, J. T., Li, Yu, Tan, Guotai, Su, Yixi, Bourdarot, Frederic, Zhao, Yang, Lynn, Jeffery W., Birgeneau, Robert J., Dai, Pengcheng
• Format: Journal Article
• Language: English
• Published: Nature Publishing Group 2020
• Subjects: Condensed Matter; Physics
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-020-19421-5

A small in-plane external uniaxial pressure has been widely used as an effective method to acquire single domain iron pnictide BaFe2As2, which exhibits twin-domains without uniaxial strain below the tetragonal-to-orthorhombic structural (nematic) transition temperature Ts. Although it is generally assumed that such a pressure will not affect the intrinsic electronic/magnetic properties of the system, it is known to enhance the antiferromagnetic (AF) ordering temperature TN ( < Ts) and create in-plane resistivity anisotropy above Ts. Here we use neutron polarization analysis to show that such a strain on BaFe2As2 also induces a static or quasi-static out-of-plane (c-axis) AF order and its associated critical spin fluctuations near TN/Ts. Therefore, uniaxial pressure necessary to detwin single crystals of BaFe2As2 actually rotates the easy axis of the collinear AF order near TN/Ts, and such effects due to spin-orbit coupling must be taken into account to unveil the intrinsic electronic/magnetic properties of the system.