Phase Transitions in LaFeAsO: Structural, Magnetic, Elastic, and Transport Properties, Heat Capacity and Mössbauer Spectra

By M. McGuire, A. Christianson, A. Sefat, B. Sales, M. Lumsden, R. Jin, E. A. Payzant, D. Mandrus, Y. Luan, V. Keppens and 6 more. 2008

213 citations recorded by the source corpus.

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 $\ensuremath{\sim}160\text{ }\text{K}$ 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 $\ensuremath{\sim}0.35{\ensuremath{\mu}}_{B}$ per iron is derived from M\"ossbauer 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.

Subfields: Accounting, Condensed Matter Physics, Electronic, Optical and Magnetic Materials

View Paper: https://www.semanticscholar.org/paper/eb70476c5863eb70bdb1941667fc8364462d39de

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Citations in the corpus

Superconductivity in iron compounds (2011, background): “…of LaFeAsO is about 0:4 memu=mole and roughly temperature independent below room temperature except for the 150 K anomaly and an upturn below 25 K. McGuire et al. (2008), with an expanded set of data for of LaFeAsO, showed that increases with increasing temperature above the anomaly up to room…”
Coherence–incoherence crossover in the normal state of iron oxypnictides and importance of Hund's rule coupling (2008, background): “In the parent compound, the resistivity exhibits a peak at 150 K [1] followed by a sharp drop, which is due to a structural transition from tetragonal (space group P4/nmm) to orthorhombic structure (space group Cmma) [3, 7] followed by a spin density wave transition [5, 6] at lower temperatures.”