Influence of the rare-earth element on the effects of the structural and magnetic phase transitions in CeFeAsO, PrFeAsO, and NdFeAsO

TL;DR

This study investigates how different rare-earth elements influence the structural and magnetic phase transitions in CeFeAsO, PrFeAsO, and NdFeAsO, revealing systematic variations in their electronic and magnetic properties.

Contribution

It provides a comparative analysis of transport and magnetic properties across the rare-earth series, highlighting the impact of rare-earth identity on phase transitions and electronic behavior.

Findings

Transport properties are strongly affected by phase transitions.

Systematic variation in Seebeck coefficient and magnetoresistance with rare-earth element.

Fe magnetic moment remains nearly constant across different Ln elements.

Abstract

We present results of transport and magnetic properties and heat capacity measurements on polycrystalline CeFeAsO, PrFeAsO, and NdFeAsO. These materials undergo structural phase transitions, spin density wave-like magnetic ordering of small moments on iron, and antiferromagnetic ordering of rare earth moments. The temperature dependence of the electrical resistivity, Seebeck coefficient, thermal conductivity, Hall coefficient, and magnetoresistance are reported. The magnetic behavior of the materials have been investigated using Mossbauer spectroscopy and magnetization measurements. Transport and magnetic properties are affected strongly by the structural and magnetic transitions, suggesting significant changes in the band structure and/or carrier mobilities occur, and phonon-phonon scattering is reduced upon transformation to the low temperature structure. Results are compared to recent reports for LaFeAsO, and systematic variations in properties as the identity of Ln is changed are observed and discussed. As Ln progresses across the rare-earth series from La to Nd, an increase in the hole contributions to Seebeck coefficient, and increases in magnetoresistance and the Hall coefficient are observed in the low temperature phase. Analysis of hyperfine fields at the iron nuclei determined from Mossbauer spectra indicates that the moment on Fe in the orthorhombic phase is nearly independent of the identity of Ln, in apparent contrast to reports of powder neutron diffraction refinements.