Magnetic Phase Transitions in NdCoAsO

TL;DR

NdCoAsO exhibits three distinct magnetic phase transitions below room temperature, involving ferromagnetic and antiferromagnetic states with varying magnetic moments, as revealed by magnetization, neutron diffraction, and physical property measurements.

Contribution

This study provides detailed characterization of the magnetic phase transitions and structures in NdCoAsO, including neutron diffraction analysis and correlation with physical properties.

Findings

Ferromagnetic transition at 69 K with small Co moments

Antiferromagnetic transition at 14 K with ordered Co and Nd moments

Further antiferromagnetic ordering at 3.5 K with larger Nd moments

Abstract

Magnetization measurements reveal that NdCoAsO undergoes three magnetic phase transitions below room temperature. The crystal and magnetic structures of NdCoAsO have been determined by powder neutron diffraction, and the effects of the phase transitions on physical properties are reported. Near 69 K a ferromagnetic state emerges with a small saturation moment of about 0.2 Bohr magnetons, likely on Co atoms. At 14 K the material enters an antiferromagnetic state with propagation vector (0 0 1/2) and small ordered moments (~0.4 Bohr magnetons) on Co and Nd. Near 3.5 K a third transition is observed, and corresponds to the antiferromagnetic ordering, with the same propagation vector, of larger moments on Nd reaching 1.30(2) Bohr magnetons at 1.4 K. In addition, transport properties and heat capacity results are presented, and show anomalies at all three phase transitions.