Detailed Study of the Phase Diagram of Fe-based Superconductor Ba(Fe1-xCox)2As2 by Super High-Resolution Neutron Diffraction Measurements. (18th March 2015)

• Record Type: Journal Article
• Authors: Ikeuchi, K; Sato, M; Li, S; Toyoda, M; Kobayashi, Y; Itoh, M; Miao, P; Torii, S; Ishikawa, Y; Kamiyama, T
• Is Part Of: Journal of physics. Number 592 (2015)
• Page Start: 012071
• Publication Date: 2015-03-18
• Subjects: Physics -- Congresses; 530.5
• DOI: 10.1088/1742-6596/592/1/012071
• Languages: English
• ISSNs: 1742-6588

Abstract

Abstract: Temperature ( T ) dependence of Bragg reflections of Ba(Fe1- x Co x )2 As2 ( x = 0, 0.02) have been measured in detail on assembled mm-size crystallites to avoid effects of surface and/or externally induced strains with the high-resolution neutron powder diffractometer, where we have found that the profile width of the (400)O /(040)O reflections with the orthorhombic indexing begin to increase, as T decreases, at ~270 K, much higher than the tetragonal (Tet)-orthorhombic (Ort) second order transition temperature T S (-147.5 K) without showing any indication of an phase change above T S . The coexistence of two Ort phases with different orthorhombicity exists in the region of ~140 K < T < 143 K). The profile widths of ( hhl )O reflections are nearly T-independent in the entire temperature region studied here (130 K ≤ T ≤ 350 K). An additional broadening due to the Co-doping is clearly found. We discuss these results in relation to the breakdown of the 4-fold symmetry of static physical quantities found in the electrical resistivity and band splitting of the 3 d yz and 3 dzx and orbitals and conclude that the disappearance of the 4-fold symmetry even in the macroscopically tetragonal phase can be understood by the existence of orthorhombic domains induced by crystal defects and/or impurities.