Two spatially separated phases in semiconducting Rb${}_{0.8}$Fe${}_{1.5}$S${}_2$

Abstract

We report neutron scattering and transport measurements on semiconducting Rb${}_{0.8}$Fe${}_{1.5}$S${}_2$, a compound isostructural and isoelectronic to the well-studied $A_{0.8}$Fe${}_y$Se${}_2(A=$ K, Rb, Cs, Tl/K) superconducting systems. Both resistivity and DC susceptibility measurements reveal a magnetic phase transition at $T=275$ K. Neutron diffraction studies show that the 275 K transition originates from a phase with rhombic iron vacancy order which exhibits an in-plane stripe antiferromagnetic ordering below 275 K. In addition, interdigitated mesoscopically with the rhombic phase is an ubiquitous phase with $\sqrt{5}\times \sqrt{5}$ iron vacancy order. This phase has a magnetic transition at $T_N=425$ K and an iron vacancy order-disorder transition at $T_S=600$ K. These two different structural phases are closely similar to those observed in the isomorphous Se materials. Based on the close similarities of the in-plane antiferromagnetic structures, moments sizes, and ordering temperatures in semiconducting Rb${}_{0.8}$Fe${}_{1.5}$S${}_2$ and K${}_{0.81}$Fe${}_{1.58}$Se${}_2$, we argue that the in-plane antiferromagnetic order arises from strong coupling between local moments. Superconductivity, previously observed in the $A_{0.8}$Fe${}_y$Se${}_{2-z}$S${}_z$ system, is absent in Rb${}_{0.8}$Fe${}_{1.5}$S${}_2$, which has a semiconducting ground state. The implied relationship between stripe/block antiferromagnetism and superconductivity in these materials as well as a strategy for further investigation is discussed in this paper.

7 pages, 5 figures

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Cited by in corpus (7)

• Sequential structural and antiferromagnetic transitions in BaFe${}_2$Se${}_3$ under pressure
• Spin waves and magnetic exchange interactions in the spin ladder compound RbFe${}_2$Se${}_3$
• Strong ferromagnetic exchange interaction in the parent state of the superconductivity in BaFe${}_2$S${}_3$
• Spin Waves and Spatially Anisotropic Exchange Interactions in the $\mathrm{S}=2$ Stripe Antiferromagnet Rb${}_{0.8}$Fe${}_{1.5}$S${}_2$
• Structural, magnetic, and electronic evolution of the spin-ladder system BaFe${}_2$S${}_{3-x}$Se${}_x$ with isoelectronic substitution
• Block antiferromagnetism and possible ferroelectricity in KFe${}_2$Se${}_2$
• Spin dynamics of the spin chain antiferromagnet RbFeS${}_2$