Mixed state properties analysis in AC magnetic field of strong pinning Fe(Se,Te) single crystal

Abstract

The fundamental harmonic of the AC magnetic susceptibility of a Fe(Se,Te) single crystal iron based superconductor has been studied at different AC field amplitudes and frequencies with and without a superimposed DC magnetic field with the aim of analyzing its superconducting properties that can be also suitable for power applications such as the critical current density and the pinning energy in AC regime. From the analysis of the fundamental Cole-Cole plots a finite influence of flux creep phenomena has been detected. Its study, by means of the Arrhenius plots, evidences thermal activation energy U values as high as 10 3 K, whose dependence on the DC and AC fields, and of the temperature, has been also obtained. The magnetic field dependence shows the existence of the strong pinning regime characterized by plastic deformations of the vortex lattice, whereas the temperature dependence of the critical current density J c (T) is consistent with the δl pinning model. Finally, the irreversibility field values H irr (T) have been extracted from the J c (T) at the different AC frequencies showing very high values if compared with the literature.

Thickness-induced crossover from strong to weak collective pinning in exfoliated FeTe$_{0.6}$Se$_{0.4}$ thin films at 1 T

“…5(b), J c at 1 T in bulk FTS is very close to that in our thin-film devices with d 100 nm. Therefore, we analyze J c (T ) using the weak collective pinning theory, as discussed for bulk FTS in previous works [4][5][6][7][8]. In the theoretical approach proposed by Griessen et al [22], J c (T ) in the moderately low field region, where the strong pinning can be ignored and the motion of single vortex is essential, is given as…”

“…Among all kinds of IBSs, the iron-based chalcogenide FeTe 1−x Se x with x = 0.4 ∼ 0.5 (FTS) has the simplest crystal structure with only FeCh (Ch = Se or Te) layers. There have been many reports on bulk [3][4][5][6][7][8][9][10][11][12] and thinfilm [13][14][15][16] FTS single crystals, which enable a detailed discussion of the pinning mechanism. Although the critical temperature T c is not so high, the upper critical field is comparable to other IBSs.…”

“…This is related to the fact that the coefficient α of the probability density for the macroscopic wave function in the Ginzburg-Landau theory is proportional to T c − T . For FTS single crystals, the pinning mechanisms have been determined by analyzing magnetization measurements with the Bean model [4][5][6][7][8]. In most cases the δl pinning is dominant [4][5][6], while in some cases both the δl and δT c pinnings coexist [7,8].…”

“…For FTS single crystals, the pinning mechanisms have been determined by analyzing magnetization measurements with the Bean model [4][5][6][7][8]. In most cases the δl pinning is dominant [4][5][6], while in some cases both the δl and δT c pinnings coexist [7,8].…”

High-Frequency ac Susceptibility of Iron-Based Superconductors

“…It is shown that a further analysis of the complex AC susceptibility data allows one to obtain the London penetration depth and therefore the superfluid density, thus enabling the validation of theories and models concerning the mechanisms of superconductivity in the IBS. For this goal, the high frequency of this technique offers an advantage with respect to conventional AC susceptometry, for which the determination of is challenging [ 16 ] because of the long wavelength and the geometry associated with those experiments [ 17 ], which is more suitable for the study of vortex physics and pinning [ 18 , 19 , 20 ] and of nonlinearity [ 21 , 22 ]. In Section 3 of this paper, we present and discuss the characterization of several IBS systems, belonging to different IBS families.…”