Doping dependence of Normal-state Property in the Iron-based Oxypnictide Superconductors LaFeAsO1-y probed by 57Fe-NMR and 75As-NMR/NQR
| Autor: | Mukuda, H., Terasaki, N., Tamura, N., Kinouchi, H., Yashima, M., Kitaoka, Y., Miyazawa, K., Shirage, P. M., Suzuki, S., Miyasaka, S., Tajima, S., Kito, H., Eisaki, H., Iyo, A. |
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| Rok vydání: | 2009 |
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| Zdroj: | J. Phys. Soc. Jpn. 78 (2009) 084717/1-7 |
| Druh dokumentu: | Working Paper |
| DOI: | 10.1143/JPSJ.78.084717 |
| Popis: | We report systematic 57Fe-NMR and 75As-NMR/NQR studies on an underdoped sample (T_c=20 K), an optimally doped sample (T_c=28 K), and an overdoped sample (T_c=22 K) of oxygen-deficient iron (Fe)-based oxypnictide superconductor LaFeAsO_{1-y}$. A microscopic phase separation between superconducting domains and magnetic domains is shown to take place in the underdoped sample, indicating a local inhomogeneity in association with the density distribution of oxygen deficiencies. As a result, 1/T_1T in the normal state of the superconducting domain decreases significantly upon cooling at both the Fe and As sites regardless of the electron-doping level in LaFeAsO_{1-y}. On the basis of this result, we claim that $1/T_1T$ is not always enhanced by antiferromagnetic fluctuations close to an antiferromagnetic phase in the underdoped superconducting sample. This contrasts with the behavior in hole-doped Ba_{0.6}K_{0.4}Fe2As2(T_c= 38 K), which exhibits a significant increase in $1/T_1T$ upon cooling. We remark that the crucial difference between the normal-state properties of LaFeAsO_{1-y} and Ba_{0.6}K_{0.4}Fe2As2 originates from the fact that the relevant Fermi surface topologies are differently modified depending on whether electrons or holes are doped into the FeAs layers. Comment: 8 pages, 13 figures, to be published in J. Phys. Soc. Jpn. Vol. 78 No. 8 |
| Databáze: | arXiv |
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