Anisotropy dependence of half-loop-mediated vortex motion in thallium-based superconductors studied by magnetoresistivity

Abstract

By measuring the temperature dependence of the magnetoresistivity, we have studied the activation energy U of two Tl-based superconducting oxides having different electronic anisotropies ͑Tl-2212, which is very anisotropic, close to Bi-2212, and Tl-1212, the anisotropy of which is about 10͒. The activation energies are described in terms of movements of half loops of vortices, with a lateral size of about the intervortex spacing a 0 . Taking into account the field dependence of the elastic coefficients C 44 and C 66 , this activation energy is estimated and compared to the experimental data. The precise magnetic-field dependence of the activation energy in Tl-2212 and Tl-1212 are different. This difference is taken into account in the frame of a single model considering two different regimes according to the anisotropy value.

Low-field vortex dynamics in various high-T c thin films

“…More interestingly, Q exhibits a clear square-root ac field dependence, which is emphasized in figure 4(top) by plotting Q H −1/2 ac vs. T . This dependence is expected for dislocation-mediated plastic flux creep where vortices propagate by protruding vortex half-loops into local energy minima in the vortex ensemble, and has previously been observed at higher fields in other anisotropic materials such as Bi 2 Sr 2 CaCu 2 O 8+x (Bi-2212) thin films, Tl 2 Ba 2 CaCu 2 O 8 (Tl-2212) single crystals [29,30] and Tl 2/3 Ba 1/3 Sr 2 CaCu 2 O 7 (Tl-1212) single crystals [30]. The barrier limiting this vortex motion is roughly given by the creation energy of a vortex-antivortex pair perpendicular to the original vortex [31] …”

Critical current-voltage scaling of heavy-ion–irradiated Bi 2 Sr 2 CaCu 2 O 8 + δ and (K,Ba)BiO 3 superconductors

“…( 1). The value of 380 is comparable to the typical values which were recently found for the overdoped (γ = 360-490), the optimally doped (γ = 550) and the slightly underdoped (γ = 800) BSCCO single crystals as well [9,17,18]. The same analysis for BPSCCO single crystals brings out a value of γ of 60 (fig.…”

“…In this letter, we present a comparative study between BSCCO, Bi 1.8 Pb 0.2 Sr 2 CaCu 2 O 8+δ (BPSCCO) and (K, Ba)BiO 3 (KBBO) compounds using the same technique as proposed before by Warmont et al [9] to determine the anisotropy factor. The Pb doping in BSCCO indeed increases the carrier concentration and causes a shift to the overdoped region in the phase diagram [10].…”

“…In order to measure the electronic anisotropy parameter γ for BSCCO and BPSCCO samples before irradiation, the angular dependence of the resistance was used before irradiation by using the same procedure as described in refs. [9,15]. Following the scaling approach from isotropic to anisotropic superconductors which was developed by Blatter et al [16], the magnetic field H at an arbitrary angle θ with respect to ab-planes, has to be scaled as follows:…”

Experimental evidence of the decoupling line in(Bi1.64Pb0.36)SrThopart1, Simon2 2001Phys. Rev. BSelf Cite3030View full textAdd to dashboardCite

“…In the linear temperature range, the extracted activation energy is then U act (T,B)ϭU 0 (B)͓1ϪT/T c ͔. For a 3D vortex loops model, 31,33 the expression of the activation energy is U loop (T,B) ϭ ͓␣ 0…”