Iron substitution in NdCoAsO: crystal structure and magnetic phase diagram

TL;DR

This study investigates how substituting Fe for Co in NdCoAsO affects its crystal structure and magnetic phases, revealing suppression of magnetic transitions and constructing a phase diagram for the system.

Contribution

It provides new insights into the structural and magnetic changes caused by Fe substitution in NdCoAsO, expanding understanding of its phase diagram.

Findings

Fe substitution increases T-As distance

Magnetic transitions are suppressed with Fe doping

Magnetic phase diagram for NdCoAsO-NdFeAsO system is constructed

Abstract

The effects of replacing small amounts of Co with Fe in NdCoAsO are reported. Polycrystalline materials with compositions NdCo1-xFexAsO (x = 0.05, 0.10, 0.15, and 0.20) are studied and the results compared to previous reports for NdCoAsO. Rietveld analysis of powder x-ray diffraction data shows that as Fe replaces Co on the transition metal (T) site, the T-As distance increases, and the As tetrahedra surrounding the T-site become more regular. Electrical resistivity and magnetization measurements indicate that the three magnetic phase transitions in NdCoAsO are suppressed as Co is replaced by Fe, and these transitions are not observed above 1.8 K for x = 0.20. Based on these results, the magnetic phase diagram for the Co-rich side of the NdCoAsO-NdFeAsO system is constructed.