Phase diagram and annealing effect for Fe_1+δTe_1−xS_xsingle crystals

Abstract

The excess Fe atoms which unavoidably exist in the Fe(Te, Se, S) crystal lattice result in a complicated antiferromagnetic ground state as well as the suppression of superconductivity. As a result, there are still discrepancies on their phase diagrams. In this paper, we report the synthesis of Fe1+δTe1-xSx (0 ≤ x ≤ 0.12) single crystals by a melting method. Superconductivity was greatly improved after air annealing by which we partially removed the excess Fe atoms. Based on the resistivity and susceptibility measurements, we concluded a phase diagram of the Fe1+δTe1-xSx (0 ≤ x ≤ 0.12) system with fewer excess iron atoms. We found a coexisting region (0.07 ≤ x ≤ 0.11) of antiferromagnetic order and bulk superconductivity. This phase diagram is similar to that of the K- or Co-doped BaFe2As2 system, as well as the Fe(Te, Se) system, implying a commonality of the iron-based superconductors.

Hydrothermal Synthesis and Transport Properties of FeS1-xTex (0 ≤ x ≤ 0.15) Single Crystals

“…The blue solid squares and the red solid circles represents T N and T c , respectively. The FeS 1-x Te x single crystals with low-S doping region were reported by a previous report [27] Fig. 4 Magnetic field dependence of the Hall resistivity for a x = 0, b x = 0.02, c x = 0.05, and d x = 0.11 single crystals at various temperatures region after the SC-I is suppressed until disappears.…”

“…For comparison, the corresponding data of FeS 1-x Te x (1 ≤ x ≤ 0.88) single crystals taken from Ref [27] are also included. For the rich-Te region, the longranged AFM phase T N gradually decreases from 70 K with increasing of S doping, and it coexists with the region of the superconducting phase (SC-II) between 0.95 and 0.89 [27], exhibiting a common property of the iron-based superconductors [22,28]. However, the phase diagram for x < 0.88 is restricted because of the solubility limitation of S. For the rich-S region on the right, superconducting (SC-I) is gradually suppressed from 4.6 K, exhibiting an approximate linear dependence on the Te content.…”

Magnetism and superconductivity of S-substituted FeTe

“…It changes from commensurate ordering with the (π, 0) propagation vector for FeTe to incommensurate one and finally the magnetic scattering is rapidly suppressed for samples with the S content ∼ 5%. Moreover, the resistivity and susceptibility measurements reveal a coexisting region of superconducting and antiferromagnetic states in the range of x ∈ (0.03, 0.1) [13,15]. Thus, the superconducting state appears in the system with the stable AFM1 phase.…”

“…Unlike the Fe(Te,Se) series, there exists the solubility limit of 30% S content in Fe(Te,S) caused by a large difference between S and Te ionic radii [16]. Previously, it was indicated that the limit is 15% S or even less [14,15], which is probably mainly the result of a difference between nominal and final compositions of studied samples. It seems that both Se and S substitutions suppress the magnetic order of FeTe thereby leading to the superconducting state.…”

“…In FeTe 1−x S x , the superconducting state appears for x = 0.03 and T c reaches the value of 10 K [12,13,14,15,16]. Unlike the Fe(Te,Se) series, there exists the solubility limit of 30% S content in Fe(Te,S) caused by a large difference between S and Te ionic radii [16].…”