Magnetic Order of the Iron Spins in NdOFeAs

TL;DR

This study reveals the antiferromagnetic order of iron spins in NdOFeAs below 141 K, showing a similar in-plane spin arrangement to other iron oxypnictides, with a notably small ordered magnetic moment.

Contribution

First detailed neutron diffraction analysis of magnetic order in NdOFeAs, identifying its magnetic structure and small ordered moment compared to related compounds.

Findings

Antiferromagnetic order below 141 K

In-plane spin arrangement similar to other iron oxypnictides

Ordered magnetic moment of 0.25 muB

Abstract

Polarized and unpolarized neutron diffraction measurements have been carried out to investigate the iron magnetic order in undoped NdOFeAs. Antiferromagnetic order is observed below 141(6) K, which is in close proximity to the structural distortion observed in this material. The magnetic structure consists of chains of parallel spins that are arranged antiparallel between chains, which is the same in-plane spin arrangement as observed in all the other iron oxypnictide materials. Nearest-neighbor spins along the c-axis are antiparallel like LaOFeAs. The ordered moment is 0.25(7) muB, which is the smallest moment found so far in these systems.