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Strong Correlations between Vacancy and Magnetic Ordering in Superconducting K0.8Fe2-ySe2



Junjie Yang, Chunruo Duan, Qingzhen Huang, Craig Brown, Joerg Neuefeind, Despina Louca


The debate of whether or not magnetic and non-magnetic phases coexist in the superconducting potassium doped iron selenide, KxFe2-ySe2, is still ongoing. With superconductivity proposed to appear in the stoichiometric, non-magnetic phase with the I4/mmm crystal symmetry, the non-superconducting phase is magnetic and with a lower symmetry, I4/m. The latter consists of Fe vacancies that go through a disordered to an ordered transition in which the partially filled Fe sites create a supercell upon ordering for which several different types have been reported The symmetry conundrum, not observed in any of the other Fe-based superconductors, has been strongly linked to the presence of superconductivity and must be resolved. Herein, we show using neutron scattering on the optimally doped composition, K0.8Fe2-ySe2, that the absence of magnetism does not signal the presence of superconductivity. Moreover, a higher degree of Fe vacancy ordering is coupled to a larger magnetic moment that coincides with a greater superconducting volume fraction.
Physical Review B


superconductivity, magnetism, neutron scattering, structure, crystallography, diffraction


Yang, J. , Duan, C. , Huang, Q. , Brown, C. , Neuefeind, J. and Louca, D. (2016), Strong Correlations between Vacancy and Magnetic Ordering in Superconducting K<sub>0.8</sub>Fe<sub>2-y</sub>Se<sub>2</sub>, Physical Review B, [online], (Accessed June 15, 2024)


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Created June 30, 2016, Updated October 12, 2021