Study of anisotropy in the superconducting properties of FeTe_0.55Se_0.45 single crystal grown by the self-flux method

Abstract

We report anisotropy in the superconducting properties of FeTe0.55Se0.45 bulk single crystal synthesized via the self-flux method. We have performed magnetotransport, magnetic and heat capacity measurements on single crystals of same batch. The grown crystals have also been characterized by XRD, XPS and Raman measurements. The superconductivity at TC ~ 14 K has been affirmed by the temperature-dependent resistivity, magnetic, and specific heat measurements. The anisotropy in upper critical field (HC2), coherence length (ξ), and critical current density (JC) have been studied from the magnetotransport and magnetic measurements, respectively, under applied magnetic fields of 0 - 12 T along the ab-plane and c-axis. The critical current density has been estimated by Bean’s critical state model at different magnetic fields (JC(H)) and temperatures (JC(T)) measured for H || ab-plane and H || c axis. The anisotropic behaviour has also been observed for JC(H). The presence of ‘peak effect’ or fishtail characteristic has been noticed in M-H loops for H || c only, which shows a shift towards the lower fields with increasing temperature. The nature of the pinning mechanisms in the sample has been determined by the normalized pinning force density using the Dew Hughes scaling rule, and the analysis of experimental data indicates the presence of δl-pinning in the sample. The temperature-dependent electronic specific heat has been fitted with the exponential law and the evaluated coupling constant 〖2∆〗_0/(k_B T_c ) is ~3.42 which is close to the universal BCS value of 3.53. The observed low value of residual Sommerfeld coefficient γ_res≈ 4.59 mJ/mol K2 indicates good quality of the grown single crystal.

Effect of thickness on the superconducting properties of the thin films of FeTe0.55Se0.45 deposited on YSZ substrates using Pulsed laser deposition (PLD) technique

“…The normalized resistivity / r r T 300 ( ) versus temperature curves, measured in the temperature range 2 K to 300 K in absence of external magnetic field, for all four thin films are shown in figure 5(a). These curves show a sharp transition in resistivity, which is consistent with the other reported results [5,12,40,43,44]. The derivative of normalised resistivity as a function of temperature is presented in the inset of figure 5 c This may be due to the smaller grain-size with weak correlation in F1 [45].…”

“…It is observed that with increasing the applied magnetic field, the observed T c shifts towards the lower temperatures which is due to the increase in magnetic flux flow in the superconducting transition region. The superconducting transition widths are increasing with the enhancement of applied magnetic field and similar broadening in the resistivity curves has been observed in other IBSs and cuprate superconductors [6,27,40,46]. The relatively small DT c for all the films, even at 12 T indicate their high upper critical fields.…”

“…The binding energy separation between Fe2p3/2, and Fe2p1/2 has a value of ∼14.00 eV, which can be clearly seen in figure 4(b). This result is quite analogous to Fe 2 O 3 [27,39,40]. For Fe2p 3/2 , the deconvoluted peak positions are at ∼ 708.29 eV and 709.97 eV, and for the Fe2p 1/2 , the peaks are deconvoluted at ∼721.99 eV and 724.59 eV.…”

Investigation on Magnetotransport Properties and Specific Heat Capacity of FeTe0.58Se0.42 Single Crystals Grown by Self‐Flux Method

“…This similar response is also observed in other FBSCs. [16,[40][41][42] Below %92 K, we have observed Fermi liquid behavior described by equation ρ ¼ ρ 0 þ AT 2 , where ρ 0 is the residual resistivity and A ¼ 1.98 nΩ cmK À2 . In the inset of Figure 3, the blue line represents the fitting of data showing Fermi liquid behavior in the temperature range 28-92 K. Similar Fermi liquid behavior has also been observed in FBSCs.…”

“…[10][11][12] Also, these FCSs are important for practical applications due to their high H C2 and J C . [13][14][15] The Fe(Te,Se) single crystals exhibit anisotropy in field-dependent transport and magnetic measurements [11,16,17] and the mixed state phenomena for different compositions. [10,[18][19][20] The thermally activated flux flow (TAFF) model has been utilized to study the vortex phase diagram of FBSCs.…”