Enhanced physical properties of single crystal Fe_0.99Te_0.63Se_0.37 prepared by self-flux synthesis method

In this study, we have systemically studied the physical, electrical and magnetic properties of Fe_0.99Te_0.63Se_0.37 single crystalline samples prepared by self-flux method. We found that the self-flux method is a suitable synthesis technique for this alloys if setting of experimental parameters made carefully. The M-H curve affirms that samples are typical type-II superconductor. Strong sign of bulk superconductivity, even after high field measurements, were seen. Calculated J_c^mag values, at zero field, were found to be 7.7 × 10⁵ Acm^-2 and 2.6 × 10⁴ Acm^-2 for 5 K and 10 K respectively. The upper critical field H_c2(0) has been determined with the magnetic field parallel to the sample surface and yielding a maximum value of 65 T. At the zero field coherence length, ξ, value was calculated to be 2.24 nm for 10% T_c^offset which is significantly larger (approximately 6 fold) than the unit cell, a, and indicating the absence of weak link behavior in the sample. Calculated μ₀H_c2(0)/k_BT_c rate indicated comparably higher value (3.66 T/K) than the Pauli limit (1.84 T/K) and obtained results were suggested unconventional nature of superconductivity in our samples.