In-plane uniaxial pressure-induced out-of-plane antiferromagnetic moment and critical fluctuations in BaFe$_2$As$_2$

Panpan Liu; Mason L. Klemm; Long Tian; Xingye Lu; Yu Song; David W. Tam; Karin Schmalzl; J. T. Park; Yu Li; Guotai Tan; Yixi Su; Frederic Bourdarot; Yang Zhao; Jeffery W. Lynn; Robert J. Birgeneau; Pengcheng Dai

doi:10.1038/s41467-020-19421-5

arXiv · 2009.04339

In-plane uniaxial pressure-induced out-of-plane antiferromagnetic moment and critical fluctuations in BaFe$_2$As$_2$

Panpan Liu·Mason L. Klemm·Long Tian·Xingye Lu·Yu Song·David W. Tam·Karin Schmalzl·J. T. Park·Yu Li·Guotai Tan·Yixi Su·Frederic Bourdarot·Yang Zhao·Jeffery W. Lynn·Robert J. Birgeneau·Pengcheng Dai

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Abstract

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 effect due to spin-orbit coupling must be taken into account to unveil the intrinsic electronic/magnetic properties of the system.

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Panpan Liu, Mason L. Klemm, Long Tian, Xingye Lu, Yu Song, David W. Tam, Karin Schmalzl, J. T. Park, Yu Li, Guotai Tan, Yixi Su, Frederic Bourdarot, Yang Zhao, Jeffery W. Lynn, Robert J. Birgeneau, Pengcheng Dai. 2020-09-09. In-plane uniaxial pressure-induced out-of-plane antiferromagnetic moment and critical fluctuations in BaFe$_2$As$_2$. https://doi.org/10.1038/s41467-020-19421-5

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