Antiferromagnetic ordering in the absence of a structural distortion in Ba(Fe{1-x}Mn{x})2As2

TL;DR

This study reveals that in Ba(Fe{1-x}Mn{x})2As2, antiferromagnetic order persists without the usual structural distortion at certain doping levels, challenging existing models of magnetoelastic coupling.

Contribution

It provides the first evidence of antiferromagnetic ordering without accompanying structural distortion in Mn-doped BaFe2As2, highlighting a unique behavior among iron arsenides.

Findings

Orthorhombic transition disappears at critical doping levels.

Magnetic order persists without structural distortion.

Unique behavior specific to Mn-doping in iron arsenides.

Abstract

Neutron and x-ray diffraction studies of Ba(Fe{1-x}Mn{x})2As2 for low doping concentrations (x <= 0.176) reveal that at a critical concentration, 0.102 < x < 0.118, the tetragonal-to-orthorhombic transition abruptly disappears whereas magnetic ordering with a propagation vector of (1/2 1/2 1) persists. Among all of the iron arsenides this observation is unique to Mn-doping, and unexpected because all models for "stripe-like" antiferromagnetic order anticipate an attendant orthorhombic distortion due to magnetoelastic effects. We discuss these observations and their consequences in terms of previous studies of Ba(Fe{1-x}TM{x})2As2 compounds (TM = Transition Metal), and models for magnetic ordering in the iron arsenide compounds.