Electronic and Magnetic Phase Diagram of a Superconductor, SmFeAsO1-xFx

A crystallographic and magnetic phase diagram of SmFeAsO1-xFx is determined as a function of x in terms of temperature based on electrical transport and magnetization, synchrotron powder x-ray diffraction, 57Fe Mossbauer spectra (MS), and 149Sm nuclear resonant forward scattering (NRFS) measurements. MS revealed that the magnetic moments of Fe were aligned antiferromagnetically at ~144 K (TN(Fe)). The magnetic moment of Fe (MFe) is estimated to be 0.34 myuB/Fe at 4.2 K for undoped SmFeAsO; MFe is quenched in superconducting F-doped SmFeAsO. 149Sm NRFS spectra revealed that the magnetic moments of Sm start to order antiferromagnetically at 5.6 K (undoped) and 4.4 K (TN(Sm)) (x = 0.069). Results clearly indicate that the antiferromagnetic Sm sublattice coexists with the superconducting phase in SmFeAsO1-xFx below TN(Sm), while antiferromagnetic Fe sublattice does not coexist with the superconducting phase.Comment: Accepted in New Journal of Physic

メスバウア ブンコウホウ ト カク キョウメイ ヒダンセイ サンランホウ オ モチイテ ノ ランタン テツ オ フクム オキシニクタイド チョウデンドウタイ ノ ケンキュウ

京都大学0048新制・課程博士博士(理学)甲第14389号理博第3386号新制||理||1496(附属図書館)UT51-2009-D101京都大学大学院理学研究科物理学・宇宙物理学専攻(主査)教授 瀬戸 誠, 教授 谷森 達, 教授 大久保 嘉高学位規則第4条第1項該当Doctor of ScienceKyoto UniversityDA

Synchrotron-Radiation-Based Mössbauer Spectroscopy

放射光でほぼ全てのメスバウアー吸収スペクトル測定が可能に - 元素を特定した電子構造や磁性の研究のプローブへ -. 京都大学プレスリリース. 2009-05-25.We have developed a new method that yields Mössbauer absorption spectra using synchrotron radiation (SR); this method is applicable for almost all Mössbauer nuclides including those that cannot be measured by previous methods using radioisotope (RI) sources. The Mössbauer spectrum of the 68.752 keV excited state of 73Ge, which cannot be measured using a RI source, was measured using SR. Our results show that this method can be used to perform advanced Mössbauer spectroscopy measurements owing to the excellent features of SR