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 Mössbauer 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 with 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 the 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 Mössbauer 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.



Keywords and Phrases

Antiferromagnetic Materials; Antiferromagnetism; Carrier Mobility; Electric Resistance; Iron Analysis; Magnetic Field Effects; Magnetic Properties; Magnetoelectronics; Magnetoresistance; Molybdenum; Phonons; Rare Earth Elements; Seebeck Coefficient; Thermal Conductivity; Anti-ferromagnetic Orderings; Electrical Resistivities; Hall Coefficients; Heat Capacity Measurements; Hyperfine Fields; Iron Nucleus; Low-temperature Phase; Low-temperature Structures; Magnetic Behaviors; Magnetic Orderings; Magnetic Transitions; Magnetization Measurements; Orthorhombic Phase; Phonon-phonon Scatterings; Poly-crystalline; Powder Neutron Diffractions; Rare-earth; Rare-earth Moments; Spin Densities; Ssbauer Spectroscopies; Structural And Magnetic Phase Transitions; Structural Phase Transitions; Systematic Variations; Temperature Dependences; Transport And Magnetic Properties; Phase Transitions

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© 2009 Institute of Physics (IOP): Open Access Journals, All rights reserved.

Publication Date

01 Feb 2009

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Chemistry Commons