Enhancement of critical current density and vortex activation energy in proton-irradiated Co-dopedBaFe2As2

Abstract

The effect of proton irradiation in Ba(Fe 0.93 Co 0.07 ) 2 As 2 single crystals is reported. We analyze temperature dependence of the current density and normalized flux relaxation rate in the framework of the collective-creep model. The glassy exponent and barrier height for flux creep are directly determined by Maley's method. Our model functions for barrier height and critical current density in the absence of flux creep are explained by the superposition of δT c and δl pinnings. We also approach true critical current density by means of the generalized inversion scheme, and the obtained result is in reasonable agreement with our model function. The proton-irradiation effect on temperature dependence of the current density and normalized relaxation rate can be summarized as doubling of the barrier height at the beginning of flux creep. PACS number(s): 74.25. Wx, 74.25.Uv, 74.25.Sv, 74.70.Xa ) 1.5 J with flux creep J c by GIS J c δl-pinning J c δT c -pinning Ba(Fe 0.93 Co 0.07 ) 2 As 2 pristine 094527-5

Magnetic relaxation and collective vortex creep in FeTe 0.6 Se 0.4 single crystal

“…4(a). The evaluated value of µ is ∼ 1.34 close to that reported in YBa 2 Cu 3 O 7−δ [33], and IBSs [10,12,20]. The value of µ resides between the prediction of singlevortex (1/7) and small-bundle (5/2) regimes, indicating that contributions of those two kinds of pinnings coexist.…”

“…Obviously, there is a plateau in the intermediate temperature range with a high vortex creep rate S ∼ 0.03. The plateau and large vortex creep rate were also observed in YBa 2 Cu 3 O 7−δ [6], and iron-based "122" [7,11,12,28] and "1111" samples [13], which can be interpreted by the collective creep theory [6]. On the other hand, S -T curve undergoes an upturn at low temperatures especially at small fields like 5 and 10 kOe.…”

“…Magnetic relaxation measurements in IBSs reported so far have revealed that they also show giant flux creep and collective pinning, which implies that IBSs and cuprate superconductors may share common vortex physics [7][8][9][10][11][12][13]. Until now, most detailed studies about the vortex dynamics on IBSs have been performed on "122" phase since high-quality single crystals are readily available.…”

“…Until now, most detailed studies about the vortex dynamics on IBSs have been performed on "122" phase since high-quality single crystals are readily available. Especially in Co-doped BaFe 2 As 2 , it shows fast flux creep and a transition from collective to plastic creep [7,9,11,12]. In order to know if the large creep rate governed by collective flux creep is an intrinsic property of IBSs, detailed vortex dynamics studies should be done on other IBS samples.…”

“…Title Here, the exponent n is set to 3/2 as in the case of YBa 2 Cu 3 O 7−δ [33,35] and Co-doped BaFe 2 As 2 [12].U = -T ln[dM (t )/d(t )]+C T, and C = ln(B ωa/2πr ) is assumed as a constant, where B is the magnetic induction, ω is the attempt frequency for vortex hopping, a is the hopping distance, and r is the sample radius. By selecting C = 18, all the curves can be scaled together as shown in Fig.…”