Effect of Fe composition on the superconducting properties (Tc, Hc2 and Hirr) of FexSe1/2Te1/2 (x = 0.95, 1.00, 1.05 and 1.10)

Abstract

In the present work, we have studied the effect of Fe composition on the superconducting properties, such as transition temperature (T c), upper critical field (H c2), and irreversibility field (H irr) of FeSe 1=2 Te 1=2. The polycrystalline samples have been prepared via solid state reaction route with nominal compositions Fe x Se 1=2 Te 1=2 (x ¼ 0.95, 1.00, 1.05 and 1.10). The x-ray diffraction results show the presence of tetragonal a-FeSe phase with the p4=nmm space group symmetry in all the samples. The zero resistance temperatures, T zero c , measured in zero magnetic field, have been found to be 10.0, 12.4, 12.3, and 11.7 K for x ¼ 0.95, 1.00, 1.05, and 1.10, respectively. The temperature dependence of H c2 (T) and H irr (T) have been calculated from the magnetoresistance data using the criteria of 90% and 10% of normal state resistivity (q n) values, respectively. The values of H c2 (0) are 121.3 T, 142.8 T, 82.7 T, and 79.3 T for x ¼ 0.95, 1.00, 1.05, and 1.10, respectively. The possible reasons for the variation of superconducting properties with Fe composition (x) have been described and discussed in this paper.

Intrinsic pinning by naturally occurring correlated defects in FeSe1−xTexsuperconductors

“…The behavior above T * is unlikely to be related to the semiconducting hexagonal phase Fe 2 Te 3 because it is also seen in pure β-phase crystals, both in the literature [20] and in our crystals. It does not have a clear and unique interpretation but it may be related with the maximum in resistivity of β-FeSe at 350 K [26].…”

“…The main features of the normal state resistivity in samples of the β-phase have been described in the literature [19,20,21,22]. A metallic like behavior was reported for the Se rich end.…”

Influence of the Fe Concentration on the Superconducting Properties of Fe $$_{1-y}$$ 1 - y Se

“…The mix of phases is possibly responsible for diverse behaviors reported in the literature for FeSe. Some authors observed that only samples near perfect stoichiometry display the highest transition temperatures [2]. Others that disorder and impurity phases enhance the superconducting properties [3].…”

First-principles Wannier function analysis of the electronic structure of PdTe: weaker magnetism and superconductivity

“…Compared with Fe-based superconductors, [3][4][5][6][7][8][9][10][11] these non-toxic layered compounds with weak interlayer van der Waals forces exhibit interesting physical properties, including phase separation, 12 strong correlations, 13,14 non-trivial isovalent doping, [15][16][17] Fe excess effects, 18 Fe vacancy, [19][20][21] and rich high-pressure phase diagrams. 13,14,[22][23][24] Attention has also shifted to other non-Fe transition metal based chalcogenides as they are shedding light on the road to the post-iron age in superconductivity.…”