Temperature dependence of iron local magnetic moment in phase-separated superconducting chalcogenide

Abstract

We have studied local magnetic moment and electronic phase separation in superconducting K${}_x$Fe${}_{2-y}$Se${}_2$ by x-ray emission and absorption spectroscopy. Detailed temperature dependent measurements at the Fe K-edge have revealed coexisting electronic phases and their correlation with the transport properties. By cooling down, the local magnetic moment of Fe shows a sharp drop across the superconducting transition temperature (T${}_c$) and the coexisting phases exchange spectral weights with the low spin state gaining intensity at the expense of the higher spin state. After annealing the sample across the iron-vacancy order temperature, the system does not recover the initial state and the spectral weight anomaly at T${}_c$ as well as superconductivity disappear. The results clearly underline that the coexistence of the low spin and high spin phases and the transitions between them provide unusual magnetic fluctuations and have a fundamental role in the superconducting mechanism of electronically inhomogeneous K${}_x$Fe${}_{2-y}$Se${}_2$ system.

6 pages, 5 figures

References in corpus (13)

• Fe-based high temperature superconductivity with Tc=31K bordering an insulating antiferromagnet in (Tl,K)FexSe2 Crystals
• Observation of Temperature-Induced Crossover to an Orbital-Selective Mott Phase in A${}_x$Fe${}_{2-y}$Se${}_2$ (A=K, Rb) Superconductors
• Transport properties of the new Fe-based superconductor KxFe2Se2 (Tc = 33 K)
• NMR Study in the Iron-Selenide Rb0.74Fe1.6Se2: Determination of the Superconducting Phase as Iron Vacancy-Free Rb0.3Fe2Se2
• Phase relations in K_xFe_{2-y}Se_2 and the structure of superconducting K_xFe_2Se_2 via high-resolution synchrotron diffraction
• Superconductivity and Magnetic Properties of high-quality single crystals of $A_x$Fe${}_2$Se${}_2$ ($A$ = K and Cs)
• Spin-state transition in the Fe-pnictides
• A study of electronic structure of FeSe${}_{1-x}$Te${}_x$ chalcogenides by Fe and Se K-edge x-ray absorption near edge structure measurements
• Spectromicroscopy of electronic phase separation in K${}_x$Fe${}_{2-y}$Se${}_2$ superconductor
• Metastable superconducting state in quenched KxFe2-ySe2
• Coexistence of different electronic phases in the K0.8Fe1.6Se2 superconductor: a bulk-sensitive hard x-rays spectroscopy study
• Large local disorder in the superconducting K_{0.8}Fe_{1.6}Se_{2} studied by extended x-ray absorption fine structure
• Effective medium approximation and the complex optical properties of the inhomogeneous superconductor K_{0.8}Fe_{2-y}Se_2

Cited by in corpus (5)

• Direct observation of nanoscale interface phase in the superconducting chalcogenide K${}_x$Fe${}_{2-y}$Se${}_2$ with intrinsic phase separation
• Local and collective magnetism of EuFe${}_2$As${}_2$
• Intermittent dynamics of antiferromagnetic phase in inhomogeneous iron-based chalcogenide superconductor
• Coexistence of $s$-wave superconductivity and phase separation in the half-filled extended Hubbard model with attractive interactions
• Fluctuating magnetism of Co- and Cu-doped NaFeAs