Spin ordering in LaFeAsO and its suppression in superconductor LaFeAsO 0:89F0:11 probed by Mössbauer spectroscopy

Shinji Kitao, Yasuhiro Kobayashi, Satoshi Higashitaniguchi, Makina Saito, Yoichi Kamihara, Masahiro Hirano, Takaya Mitsui, Hideo Hosono, Makoto Seto

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Abstract

57Fe Mössbauer spectroscopy was applied to an iron-based layered superconductor LaFeAsO0:89F0:11 with a transition temperature of 26K and to its parent material LaFeAsO. Throughout the temperature range from 4.2 to 298 K, a singlet pattern with no magnetic splitting was observed in the Mössbauer spectrum of the F-doped superconductor. Furthermore, no additional internal magnetic field was observed for the spectrum measured at 4.2K under a magnetic field of 7 T. On the other hand, magnetically split spectra were observed in the parent LaFeAsO below 140 K, and this temperature is slightly lower than that of a structural phase transition from tetragonal to orthorhombic phase, which accompanies the electrical resistivity anomaly at around 150 K. The magnetic moment is estimated to be ∼0:35 μB/Fe from the internal magnetic field of 5.3 T at 4.2K in the orthorhombic phase, and the spin disorder appears to remain in the magnetically ordered state even at 4.2 K. The lack of a magnetic transition in LaFeAsO0:89F0:11 down to 4.2K suggests that this system exhibits a paramagnetic state or that the magnetic moment is small. The present results show that F doping effectively suppresses the magnetic and structural transitions in the parent material, leading to the emergence of superconductivity in the F-doped system.

Original languageEnglish
Article number103706
JournalJournal of the Physical Society of Japan
Volume77
Issue number10
DOIs
Publication statusPublished - 2008 Oct 1
Externally publishedYes

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Keywords

  • F doping
  • Fe Mössbauer spectroscopy
  • LaFeAso
  • LaFeAso F
  • Magnetic moment
  • Superconductivity

ASJC Scopus subject areas

  • Physics and Astronomy(all)

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