### 抜粋

We report experimental results of ^{75}As and ^{139}La nuclear magnetic resonance (NMR) in the layered oxypnictide system LaFeAs (O_{1 - x} F_{x}) (x = 0.0, 0.04, 0.07 and 0.11) where superconductivity occurs in x greater than 0.04. In the undoped LaFeAsO, 1 / T_{1} of ^{139}La exhibits a distinct peak at T_{N} ~ 142 K below which the La NMR spectra become broadened due to the internal magnetic field attributed to an antiferromagnetic (AFM) ordering. In the x = 0.04 sample, 1 / T_{1} T of ^{75}As exhibits a Curie-Weiss temperature dependence down to 30 K, suggesting the development of AFM spin fluctuations with decreasing temperature. In the x = 0.11 sample, in contrast, pseudogap behavior is observed in 1 / T_{1} T at the ^{75}As site with a gap value of Δ_{PG} ~ 175 K. The spin dynamics vary markedly with F-doping, which is ascribed to the change of the Fermi-surface structure by the electron-doping. As for the superconducting properties for x = 0.04, 0.07 and 0.11, 1 / T_{1} of ^{75}As in all compounds does not exhibit a coherence peak just below T_{c} and follows a T^{3} dependence at low temperatures. These results seemingly suggests that unconventional superconductivity with zero gap along lines, whereas the lack of the residual density of states at the low temperatures is incompatible with the presence of the line-nodes. We discuss similarity and difference between LaFeAs (O_{1 - x} F_{x}) and cuprates, and also discuss the relationship between spin dynamics and superconductivity on the basis of F-doping dependence of T_{c} and 1 / T_{1}. Crown

元の言語 | English |
---|---|

ページ（範囲） | 3089-3094 |

ページ数 | 6 |

ジャーナル | Physica B: Condensed Matter |

巻 | 404 |

発行部数 | 19 |

DOI | |

出版物ステータス | Published - 2009 10 15 |

外部発表 | Yes |

### ASJC Scopus subject areas

- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Electrical and Electronic Engineering

## フィンガープリント <sup>75</sup>As and <sup>139</sup>La NMR studies on LaFeAs (O<sub>1 - x</sub> F<sub>x</sub>)' の研究トピックを掘り下げます。これらはともに一意のフィンガープリントを構成します。

## これを引用

^{75}As and

^{139}La NMR studies on LaFeAs (O

_{1 - x}F

_{x}).

*Physica B: Condensed Matter*,

*404*(19), 3089-3094. https://doi.org/10.1016/j.physb.2009.07.078