Large-moment antiferromagnetic order in overdoped high-<i>T</i><sub>c</sub> superconductor <sup>154</sup>SmFeAsO<sub>1-<i>x</i></sub> D <sub><i>x</i></sub>.
basic_science · Level V
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- Record sourced from PubMed, PMID 28507123.
- Also identified by DOI 10.1073/pnas.1703295114 and PMC identifier 5465885.
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Abstract
In iron-based superconductors, high critical temperature (<i>T</i><sub>c</sub>) superconductivity over 50 K has only been accomplished in electron-doped <i>hRE</i>FeAsO (<i>hRE</i> is heavy rare earth (<i>RE</i>) element). Although <i>hRE</i>FeAsO has the highest bulk <i>T</i><sub>c</sub> (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 <sup>154</sup>SmFeAsO<sub>1-<i>x</i></sub> D <sub><i>x</i></sub> , and the discovery of a long-range antiferromagnetic ordering with <i>x</i> ≥ 0.56 (AFM2) accompanying a structural transition from tetragonal to orthorhombic. Surprisingly, the Fe magnetic moment in AFM2 reaches a magnitude of 2.73 μ<sub>B</sub>/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-3<i>d</i><sub><i>xy</i></sub> orbital, in which the nearest-neighbor hopping parameter becomes zero. The unique phase diagram, i.e., highest-<i>T</i><sub>c</sub> superconducting phase adjacent to the strongly correlated phase in electron-overdoped regime, yields important clues to the unconventional origins of superconductivity.