Large-moment antiferromagnetic order in overdoped high-T c superconductor 154SmFeAsO1−xDₓ

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 114; no. 22; pp. E4354 - E4359
• Main Authors: Iimura, Soshi, Okanishi, Hiroshi, Matsuishi, Satoru, Hiraka, Haruhiro, Honda, Takashi, Ikeda, Kazutaka, Hansen, Thomas C., Otomo, Toshiya, Hosono, Hideo
• Format: Journal Article
• Language: English
• Published: National Academy of Sciences 30.05.2017
• ISSN: 0027-8424; 1091-6490

In iron-based superconductors, high critical temperature (T c) superconductivity over 50 K has only been accomplished in electron-doped hREFeAsO (hRE is heavy rare earth (RE) element). Although hREFeAsO has the highest bulk T c (58 K), progress in understanding its physical properties has been relatively slow due to difficulties in achieving high-concentration electron doping and carrying out neutron experiments. Here, we present a systematic neutron powder diffraction study of 154SmFeAsO1−xDₓ, and the discovery of a long-range antiferromagnetic ordering with x ≥ 0.56 (AFM2) accompanying a structural transition from tetragonal to orthorhombic. Surprisingly, the Fe magnetic moment in AFM2 reaches a magnitude of 2.73 μB/Fe, which is the largest in all nondoped iron pnictides and chalcogenides. Theoretical calculations suggest that the AFM2 phase originates in kinetic frustration of the Fe-3dxy orbital, in which the nearest-neighbor hopping parameter becomes zero. The unique phase diagram, i.e., highest-T c superconducting phase adjacent to the strongly correlated phase in electron-overdoped regime, yields important clues to the unconventional origins of superconductivity.