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

Published

July 1, 2016

Author(s)

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

Abstract

The debate of whether or not magnetic and non-magnetic phases coexist in the superconducting potassium doped iron selenide, K_xFe_2-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, K_0.8Fe_2-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.

Citation

Physical Review B

Volume

94

Issue

2

Pub Type

Journals

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Keywords

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

Citation

Yang, J. , Duan, C. , Huang, Q. , Brown, C. , Neuefeind, J. and Louca, D. (2016), Strong Correlations between Vacancy and Magnetic Ordering in Superconducting K_0.8Fe_2-ySe₂, Physical Review B, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=919421 (Accessed October 31, 2025)