The evolution of antiferromagnetic susceptibility to uniaxial pressure in Ba(Fe{1-x}Co{x})2As2

TL;DR

This study investigates how uniaxial pressure affects magnetic and structural transitions in Ba(Fe{1-x}Co{x})2As2, revealing pressure-induced shifts and decoupling phenomena that inform models of nematic susceptibility in iron pnictides.

Contribution

It provides new experimental data on the effects of uniaxial pressure on magnetic and structural order parameters in doped BaFe2As2, especially near the tricritical point.

Findings

Uniaxial pressure shifts the antiferromagnetic transition temperature.

Decoupling of structural and magnetic transitions occurs under pressure.

Pressure effects become more pronounced as Co-doping increases.

Abstract

Neutron diffraction measurements are presented measuring the responses of both magnetic and structural order parameters of parent and lightly Co-doped Ba(Fe{1-x}Co{x})2As2 under the application of uniaxial pressure. We find that the uniaxial pressure induces a thermal shift in the onset of antiferromagnetic order that grows as a percentage of T_N as Co-doping is increased and the superconducting phase is approached. Additionally, as uniaxial pressure is increased within parent and lightly-doped Ba(Fe{1-x}Co{x})2As2 on the first order side of the tricritical point, we observe a decoupling between the onsets of the orthorhombic structural distortion and antiferromagnetism. Our findings place needed constraints on models exploring the nematic susceptibility of the bilayer pnictides in the tetragonal, paramagnetic regime.