Superconducting, magnetic and magnetotransport properties of FeTe1-xSex single crystals

Rohit Kumar,G D Varma,Sudesh Sudesh

doi:10.1063/1.5007291

Abstract

The single crystalline samples with compositions FeTe1-xSex (0.25 ≤ x ≤ 0.50) have been prepared via self-flux method and the superconducting, magnetic and magnetotransport properties of the grown crystals were investigated. The superconducting onset temperatures have been determined from the measurements of zero field cooled magnetization and resistance with temperatures. In the present case, highest superconducting transition temperature TC (onset) ∼ 15 K has been obtained for x=0.5. The HC2 (T=0 K) values have been estimated by fitting the experimental HC2 - T plots with WHH model. The highest HC2(0) has been obtained for x=0.5. The activation energy of the thermally activated flux flow has been found from the broadening of superconducting transition in an applied magnetic field using the Arrhenius law. Our results show that the activation energy (U0) decreases with the increasing magnetic field. Furthermore, the magnetization measurements for x=0.4 and 0.5 samples have been performed at T=5 K in the magnetic field range ±7 T to estimate critical current density at different applied magnetic fields using Bean formula. We see that the sample x=0.5 has higher values of JC as compared to that of x=0.4 at all magnetic fields. This is in conformity with the behavior of U0–H plots.

Highlights

FeSe(Te), which belongs to the Fe-based family of superconducting compounds, has the simplest crystal structure.[1,2,3,4,5,6] It consists of only the continuous stacking of tetrahedral Fe(Se/Te)[4] layers arranged along the c-axis
The powder X-ray diffraction (XRD) results show that all samples have tetragonal crystal structure with the space group P4/nmm
The zero field cooling (ZFC)- field cooling (FC) curves show a magnetic anomaly for all samples which occurs at 126±5 K possibly due to presence of impurity phase Fe7Se8

Summary

INTRODUCTION

FeSe(Te), which belongs to the Fe-based family of superconducting compounds, has the simplest crystal structure.[1,2,3,4,5,6] It consists of only the continuous stacking of tetrahedral Fe(Se/Te)[4] layers arranged along the c-axis. It is observed that this structural phase transition depends on the amount of excess Fe present in the compound.[20,21,22] Unlike pnictides, the application of pressure as high as 19 GPa does not lead to the emergence of superconductivity in FeTe but the structural phase transition shifts towards lower temperatures.[17,18] chemical doping at the Te-site in Fe1+yTe system with Se gives rise to superconductivity.[7,8,9,23,24,25,26,27] Highest TC (∼15 K) is observed when Se substitutes for Te in FeTe system with the composition FeTe1-xSex (x = 0.5).[7,8,9,28]. The samples are grown with compositions FeTe1-xSex (0.25 ≤ x ≤ 0.50)

EXPERIMENTAL DETAILS

RESULTS AND DISCUSSION

CONCLUSIONS