In-plane uniaxial pressure-induced out-of-plane antiferromagnetic moment and critical fluctuations in BaFe2As2

• Published in: Nature communications Vol. 11; no. 1; p. 5728
• 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, Frédéric, Zhao, Yang, Lynn, Jeffery W., Birgeneau, Robert J., Dai, Pengcheng
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 12.11.2020; Nature Publishing Group; Nature Portfolio
• Subjects: 639/766/119/1003; 639/766/119/997; Anisotropy; Antiferromagnetism; CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; Crystals; Domains; Experiments; External pressure; Fluctuations; Group 5A compounds; Humanities and Social Sciences; Iron; Magnetic properties; Magnetic properties and materials; Magnetism; multidisciplinary; Neutrons; NMR; Nuclear magnetic resonance; Phase transitions; Physics; Polarization; Pressure; Science; Science (multidisciplinary); Single crystals; Spin-orbit interactions; superconducting properties and materials; Superconductors; Transition temperature; Transition temperatures
• 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 BaFe 2 As 2 , which exhibits twin-domains without uniaxial strain below the tetragonal-to-orthorhombic structural (nematic) transition temperature T s . 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 T N ( <  T s ) and create in-plane resistivity anisotropy above T s . Here we use neutron polarization analysis to show that such a strain on BaFe 2 As 2 also induces a static or quasi-static out-of-plane ( c -axis) AF order and its associated critical spin fluctuations near T N / T s . Therefore, uniaxial pressure necessary to detwin single crystals of BaFe 2 As 2 actually rotates the easy axis of the collinear AF order near T N / T s , and such effects due to spin-orbit coupling must be taken into account to unveil the intrinsic electronic/magnetic properties of the system. BaFe 2 As 2 is a parent compound for iron based superconductors, and this has motivated extensive study of its magnetic and electronics properties. Here, using neutron polarisation analysis, the authors demonstrate the critical importance of spin-orbit coupling to properties of BaFe 2 As 2 .