Crystallographic Phase Transition and High-Tc Superconductivity in LaFeAsO:F

Takatoshi Nomura; Sung Wng Kim; Yoichi Kamihara; Masahiro Hirano; Peter V. Sushko; Kenichi Kato; Masaki Takata; Alexander L. Shluger; Hideo Hosono

doi:10.1088/0953-2048/21/12/125028

arXiv · 0804.3569

Crystallographic Phase Transition and High-Tc Superconductivity in LaFeAsO:F

Takatoshi Nomura·Sung Wng Kim·Yoichi Kamihara·Masahiro Hirano·Peter V. Sushko·Kenichi Kato·Masaki Takata·Alexander L. Shluger·Hideo Hosono

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Abstract

Undoped LaFeAsO, parent compound of the newly found high-Tc superconductor, exhibits a sharp decrease in the temperature-dependent resistivity at ~160 K. The anomaly can be suppressed by F doping and the superconductivity appears correspondingly, suggesting a close associate of the anomaly with the superconductivity. We examined the crystal structures, magnetic properties and superconductivity of undoped (normal conductor) and 14 at.% F-doped LaFeAsO (Tc = 20 K) by synchrotron X-ray diffraction, DC magnetic measurements, and ab initio calculations to demonstrate that the anomaly is associated with a phase transition from tetragonal (P4/nmm) to orthorhombic (Cmma) phases at ~160 K as well as an antiferromagnetic transition at ~140 K. These transitions can be explained by spin configuration-dependent potential energy surfaces derived from the ab initio calculations. The suppression of the transitions is ascribed to interrelated effects of geometric and electronic structural changes due to doping by F- ions.

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Takatoshi Nomura, Sung Wng Kim, Yoichi Kamihara, Masahiro Hirano, Peter V. Sushko, Kenichi Kato, Masaki Takata, Alexander L. Shluger, Hideo Hosono. 2008-11-12. Crystallographic Phase Transition and High-Tc Superconductivity in LaFeAsO:F. https://doi.org/10.1088/0953-2048%2F21%2F12%2F125028

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