Study of Structural and Magnetotransport Properties of Fe(Te, Se) Single Crystals

Abstract

Single‐crystalline samples of nominal compositions FeTe0.88 and FeTe1−xSex are synthesized using the self‐flux method. The activation energy of the flux flow is estimated using the Arrhenius relation as well as by the modified thermally activated flux flow (TAFF) model. The field dependence of U0 shows transition from single to collective vortex pinning at a magnetic field of ≈2 T. The analysis of field‐dependent U0 data reveals the planar and the point defect magnetic field regions for both the models. The modified TAFF model is used to study the 2D and 3D behavior of the vortex state for all the superconducting samples. The single‐crystalline FeTe0.80Se0.20 and FeTe0.60Se0.40 samples show 3D behavior, whereas the FeTe0.40Se0.60 crystal shows 2D behavior. The vortex phase diagrams of all the superconducting samples are obtained by analyzing the magnetotransport data. The vortex phase diagrams reveal transitions from the unpinned to pinned vortex liquid state and the vortex liquid to vortex glass state. Below T*, the critical exponent s is in good agreement with q values for 2D/3D behavior of vortex states of all the superconducting samples.

Chemical Vapor Deposition of Superconducting FeTe1–xSex Nanosheets

“…The enlarged segments of the (001) reflections are also presented in Figure . When x in FeTe 1– x Se x increases, the (001) peaks shift to larger 2θ values, which is consistent with the fact that the interlayer spacing decreases with increasing amounts of Se . The full width at half-maximum (fwhm) values, δ­(2θ), of all the samples are in the range of 0.13 to 0.37°, demonstrating the relatively uniform compositional distribution of FeTe 1– x Se x (Figure S3).…”

“…When x in FeTe 1−x Se x increases, the (001) peaks shift to larger 2θ values, which is consistent with the fact that the interlayer spacing decreases with increasing amounts of Se. 20 The full width at half-maximum (fwhm) values, δ(2θ), of all the samples are in the range of 0.13 to 0.37°, demonstrating the relatively uniform compositional distribution of FeTe 1−x Se x (Figure S3). To highlight, precise control over the reaction temperature of chalcogen precursors is critical to achieving a high purity of the tetragonal phase of the products.…”

“…The FeTe 1– x Se x samples for XRD measurements were prepared at a reaction temperature of 550 °C. The composition of the sample was determined by the peak position of the [001] reflection, taking lattice constant c of FeTe to be 0.628 nm and c of FeTe 0.5 Se 0.5 to be 0.599 nm according to ref .…”

Temporal Spinodal Decomposition of the Fe1+yTe1−xSex Crystals and its Impact on Superconducting Properties

“…The literary data are shown by blue squares with letters corresponding to studies as follows: D, [ 13 ] M, [ 28 ] O, [ 27 ] R, [ 29 ] S, [ 1 ] V, [ 30 ] X, [ 31 ] Ka, [ 32 ] Ku. [ 33 ] Color intensity correlates with excess iron content: light blue is for y < 0.05and dark blue is for y > 0.10. Green straight line is drawn over the literature data for x °< 0.4.…”

“…This fact has already been noted in a number of articles, in particular in the study by Onoda et al [27] The magenta dotted line (Figure 5), corresponding to this equation, is noticeably below all experimental points. We use the following parameters for plotting this line: [ 27 ] and [ 33 ] .…”