Phase transitions in LaFeAsO: Structural, magnetic, elastic, and transport properties, heat capacity and Mössbauer spectra

McGuire, M. A.; Sougrati, M. T.; Christianson, A. D.; Brill, J. W.; Hermann, R. P.; Lumsden, M. D.; Long, G.; Sales, B. C.; Grandjean, F.; Payzant, E. A.; Luan, Y.; Mandrus, D.; Keppens, V.; Jin, R.; Varadarajan, V.; Sefat, A. S.

doi:10.1103/PhysRevB.78.094517

Journal Article

Phase transitions in LaFeAsO: Structural, magnetic, elastic, and transport properties, heat capacity and Mössbauer spectra

McGuire, M. A. ; Christianson, A. D. ; Sefat, A. S. ; Sales, B. C. ; Lumsden, M. D. ; Jin, R. ; Payzant, E. A. ; Mandrus, D. ; Luan, Y. ; Keppens, V. ; Varadarajan, V. ; Brill, J. W. ; Hermann, R. P.FZJ* ; Sougrati, M. T. ; Grandjean, F. ; Long, G.

2008
APS College Park, Md.

Physical review / B 78(9), 094517 (2008) [10.1103/PhysRevB.78.094517]

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Please use a persistent id in citations: http://hdl.handle.net/2128/11081 doi:10.1103/PhysRevB.78.094517

Abstract: We present results from a detailed experimental investigation of LaFeAsO, the parent material in the series of "FeAs" based oxypnictide superconductors. Upon cooling, this material undergoes a tetragonal-orthorhombic crystallographic phase transition at similar to 160 K followed closely by an antiferromagnetic ordering near 145 K. Analysis of these phase transitions using temperature dependent powder x-ray and neutron-diffraction measurements is presented. A magnetic moment of similar to 0.35 mu(B) per iron is derived from Mossbauer spectra in the low-temperature phase. Evidence of the structural transition is observed at temperatures well above the transition temperature (up to near 200 K) in the diffraction data as well as the polycrystalline elastic moduli probed by resonant ultrasound spectroscopy measurements. The effects of the two phase transitions on the transport properties (resistivity, thermal conductivity, Seebeck coefficient, and Hall coefficient), heat capacity, and magnetization of LaFeAsO are also reported, including a dramatic increase in the magnitude of the Hall coefficient below 160 K. The results suggest that the structural distortion leads to a localization of carriers on Fe, producing small local magnetic moments which subsequently order antiferromagnetically upon further cooling. Evidence of strong electron-phonon interactions in the high-temperature tetragonal phase is also observed.

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Physics, Condensed Matter

Note: We acknowledge useful discussions with D. J. Singh, O. Garlea, S. Nagler, A. Castro-Neto, and I. I. Mazin, and technical assistance by J. Zarestky and J. Fernandez-Baca. Research sponsored by the Division of Materials Sciences and Engineering, Office of Basic Energy Sciences. Part of this research performed by Eugene P. Wigner Fellows at ORNL, managed by UT-Battelle, LLC, for the U. S. DOE under Contract No. DE-AC05-00OR22725. A portion of this research at ORNL's Center for Nanophase Materials Sciences and High Flux Isotope Reactor was sponsored by the Scientific User FacilitiesDivision, Office of Basic Energy Sciences, DOE. A portion of this work was supported by NSF Grant No. DMR-0400938. F.G. acknowledges with thanks the financial support of the Fonds National de la Recherche Scientifique, Belgium, through Grants No. 9.456595 and No. 1.5.064.05.

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Appears in the scientific report 2008

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