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This article reviews recent experimental investigations on two binary Fe-chalcogenides: FeSe and Fe$_{1+y}$Te. The main focus is on synthesis, single crystal growth, chemical composition, as well as on the effect of excess iron on…

We have synthesized polycrystalline samples and single crystals of Fe(Te1-xSx)y, and characterized their properties. Our results show that the solid solution of S in this system is limited, < 30%. We observed superconductivity at ~ 9 K in…

Among iron based superconductors, the layered iron chalcogenide Fe(Te1-xSex) is structurally the simplest and has attracted considerable attentions. It has been speculated from bulk studies that nanoscale inhomogeneous superconductivity may…

We report our study of the evolution of superconductivity and the phase diagram of the ternary Fe(Se1-xTex)0.82 (0<=x<=1.0) system. We discovered a new superconducting phase with Tc,max = 14 K in the 0.3 < x < 1.0 range. This…

The iron chalcogenide Fe$_{1+y}$Te$_{1-x}$Se$_{x}$ on the Te-rich side is known to exhibit the strongest electron correlations among the Fe-based superconductors, and is non-superconducting for $x$ < 0.1. In order to understand the origin…

We investigated the evolution of the temperature-composition phase diagram of Fe$_{1+y}$Te upon Se substitution. In particular, the effect of Se substitution on the two-step, coupled magneto-structural transition in Fe$_{1+y}$Te single…

We report investigation on Fe1+yTexSe1-x single crystals by using scanning transmission electron microscopy (STEM) and electron energy loss spectroscopy (EELS). Both nonsuperconducting samples with excess iron and superconducting samples…

In this paper, we address a number of outstanding issues concerning the nature and the role of magnetic inhomogenities in the iron chalcogenide system FeTe1-xSex and their correlation with superconductivity in this system. We report…

The superconducting and magnetic properties of Fe$_{y}$Se$_{0.25}$Te$_{0.75}$ single crystals ($0.9\leq y \leq1.1$) were studied by means of x-ray diffraction, SQUID magnetometry, muon spin rotation, and elastic neutron diffraction. The…

Iron chalcogenide Fe(Te,Se) attracted much attention due to its simple structure, which is favorable for probing the superconducting mechanism. Its less toxic nature compared with iron arsenides is also advantageous for applications of…

Superconducting iron chalcogenide FeSe has the simplest crystal structure among all the Fe-based superconductors. Unlike other iron pnictides, FeSe exhibits no long range magnetic order accompanying the tetragonal-to-orthorhombic structural…

[(Li0.8Fe0.2)OH]FeS and the series [(Li0.8Fe0.2)OH]Fe(S1-xSex) (0<x<1) were synthesized by hydrothermal methods and characterized by X-ray single crystal and powder diffraction, EDX and chemical analysis. Selenium-rich compounds show the…

The level of electronic correlation has been one of the key questions in understanding the nature of superconductivity. Among the iron-based superconductors, the iron chalcogenide family exhibits the strongest electron correlations. To…

Recent investigations have shown that Fe$_{1+y}$Te$_{1-x}$Se$_{x}$ can be made superconducting by annealing it in Se and O vapors. The current lore is that these chalcogen vapors induce superconductivity by removing the magnetic excess Fe…

Structure and composition of iron chalcogenides have a delicate relationship with magnetism and superconductivity. In this report we investigate the iron sulfide layered tetragonal phase (t-FeS), and compare with three-dimensional hexagonal…

We have investigated the influence of Fe-excess on the electrical transport and magnetism of Fe1+yTe0.5Se0.5 (y=0.04 and 0.09) single crystals. Both compositions exhibit resistively determined superconducting transitions (Tc) with an onset…

Magnetic properties of iron chalcogenide superconducting materials are investigated using density functional calculations. We find the stability of magnetic phases is very sensitive to the height of chalcogen species from the Fe plane:…

Superconductivity in anti-PbO-type iron chalcogenides Fe1-xTe1-ySey (x = 0, 0.1, y = 0.1 0.4) depends on the amount (x) of interstitial iron atoms located between the FeTe1-ySey layers. Non-superconducting samples of nominal Fe1.1Te1-ySey…

Less than two years after the discovery of high temperature superconductivity in oxypnictide LaFeAs(O,F) several families of superconductors based on Fe layers (1111, 122, 11, 111) are available. They share several characteristics with…

We report on the first local atomic structure study via the pair density function (PDF) analysis of neutron diffraction data and show a direct correlation of local coordinates to TC in the newly discovered superconducting FeSe1-xTex. The…