Anisotropic magnetism, superconductivity, and the phase diagram of Rb(1-x)Fe(2-y)Se2

Abstract

We report the crystal growth and structural, magnetic, conductivity, and specific heat investigations of Rb(1-x)Fe(2-y)Se2 single crystals with varying stoichiometry prepared by self-flux and Bridgman methods. The system exhibits a strongly anisotropic antiferromagnetic behavior below 400 K. For 1.53 <2-y< 1.6 superconductivity is found, whereas for Fe concentrations 2-y< 1.5 and 2-y> 1.6 insulating and semiconducting behavior is observed, respectively. The sharpest transition to the superconducting state and the highest transition temperature T_c of 32.4 K is found for compositions close to Rb2Fe4Se5. A critical current density j_c of 1.6*10^4 A/cm^2 (at 2 K) is obtained in the superconducting samples with the highest diamagnetic response. In these samples additional intense x-ray reflexes appear, which are incompatible with the tetragonal symmetry. Upper critical fields H_{c2} of ~250 kOe for the in-plane and 630 kOe for the inter-plane configurations are estimated from resistivity in magnetic fields parallel and perpendicular to the c-axis, respectively. In the non-superconducting samples with the Fe concentration below 1.45 both specific heat and susceptibility revealed an anomaly at 220 K which is not related to antiferromagnetic or structural transformations. Comparison with the magnetic behavior of non-superconducting samples provides evidence for the coexistence of superconductivity and static antiferromagnetic order.

12 pages, 16 figures, 2 tables

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• Optical conductivity of iron-based superconductors
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• Interplay between Superconductivity and Magnetism in Rb0.8Fe1.6Se2 under Pressure
• Superconductivity and magnetism in RbxFe2-ySe2: Impact of thermal treatment on mesoscopic phase separation
• High resolution characterisation of microstructural evolution in Rb${}_x$Fe${}_{2-y}$Se${}_2$ crystals on annealing
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• High-pressure study of superconducting and non-superconducting single crystals of the same nominal composition Rb0.8Fe2Se2
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• Field-induced transition of the magnetic ground state from A-type antiferromagnetic to ferromagnetic order in CsCo2Se2
• Structure, superconductivity, and magnetism in Rb1-xFe1.6Se2-zSz
• Tuning orbital-selective correlation effects in superconducting Rb${}_{0.75}$Fe${}_{1.6}$Se${}_{2-z}$S${}_z$
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• Connection between ambient-pressure and pressure-induced superconducting phases in alkaline iron selenide superconductors
• Quenching Dependence on Superconductivity in the Synthesizing Process of Single Crystals of Rb${}_x$Fe${}_{2-y}$Se${}_2$
• Phase separation in iron chalcogenide superconductor Rb0.8+xFe1.6+ySe2 as seen by Raman light scattering and band structure calculations