Local breaking of four-fold rotational symmetry by short-range magnetic order in heavily overdoped Ba(Fe$_{1-x}$Cu$_{x}$)$_{2}$As$_{2}$

TL;DR

This study reveals that heavily Cu-doped Ba(Fe$_{1-x}$Cu$_x$)$_2$As$_2$ exhibits short-range stripe magnetic order and local four-fold symmetry breaking, even without long-range magnetic order, highlighting the ubiquity of stripe magnetism in iron pnictides.

Contribution

It demonstrates the persistence of short-range magnetic order and local symmetry breaking in heavily overdoped Ba(Fe$_{1-x}$Cu$_x$)$_2$As$_2$, expanding understanding of magnetic phenomena in iron pnictides.

Findings

Short-range stripe magnetic order persists over a large doping range.

Local four-fold rotational symmetry is broken in the heavily doped regime.

Cu acts as vacancies that relieve magnetic frustration.

Abstract

We investigate Cu-doped Ba(Fe$_{1-x}$Cu$_x$)$_2$As$_2$ with transport, magnetic susceptibility, and elastic neutron scattering measurements. In the heavily Cu-doped regime where long-range stripe-type antiferromagnetic order in BaFe$_2$As$_2$ is suppressed, Ba(Fe$_{1-x}$Cu$_x$)$_2$As$_2$ (0.145 $\leq x \leq$ 0.553) samples exhibit spin-glass-like behavior in magnetic susceptibility and insulating-like temperature dependence in electrical transport. Using elastic neutron scattering, we find stripe-type short-range magnetic order in the spin-glass region identified by susceptibility measurements. The persistence of short-range magnetic order over a large doping range in Ba(Fe$_{1-x}$Cu$_x$)$_2$As$_2$ likely arises from local arrangements of Fe and Cu that favor magnetic order, with Cu acting as vacancies relieving magnetic frustration and degeneracy. These results indicate locally broken four-fold rotational symmetry, suggesting that stripe-type magnetism is ubiquitous in iron pnictides.