Interplay between Fe and Nd magnetism in NdFeAsO single crystals

TL;DR

This study investigates the complex magnetic and structural phase transitions in NdFeAsO single crystals, revealing unique magnetic order changes and interactions between Fe and Nd moments through neutron and x-ray diffraction analyses.

Contribution

It provides new insights into the interplay between Fe and Nd magnetism and the phase transition behaviors in NdFeAsO, highlighting differences from related compounds.

Findings

Fe moments order AFM in stripe-like structure

Fe magnetic order changes from AFM to FM along c below T*

Nd moments order AFM below T_Nd

Abstract

The structural and magnetic phase transitions have been studied on NdFeAsO single crystals by neutron and x-ray diffraction complemented by resistivity and specific heat measurements. Two low-temperature phase transitions have been observed in addition to the tetragonal-to-orthorhombic transition at T_S = 142 K and the onset of antiferromagnetic (AFM) Fe order below T_N = 137 K. The Fe moments order AFM in the well-known stripe-like structure in the (ab) plane, but change from AFM to ferromagnetic (FM) arrangement along the c direction below T* = 15 K accompanied by the onset of Nd AFM order below T_Nd = 6 K with this same AFM configuration. The iron magnetic order-order transition in NdFeAsO accentuates the Nd-Fe interaction and the delicate balance of c-axis exchange couplings that results in AFM in LaFeAsO and FM in CeFeAsO and PrFeAsO.