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The vortex dynamics of Bi 2 Sr 2 Ca 1−x Gd x Cu 2 O 8+δ single crystals is investigated by magnetic relaxation and hysteresis measurements. By substituting Ca with Gd, it is found that the interlayer Josephson coupling is weakened and the anisotropy is increased, which leads to the change of vortex dynamics from 3D elastic to 2D plastic vortex creep. Moreover, the second magnetization peak, which can be observed in samples near the optimal doping, is absent in the strongly underdoped ( with 2D vortex ) region.

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“…Similar results on Bi 2 Sr 2 Ca 1−x Gd x Cu 2 O 8+δ single crystals are reported by other authors [11].…”

Section: Second Peaksupporting

confidence: 80%

Dimensional crossover of vortex dynamics induced by Gd substitution on Bi2212 single crystals

Zhao

Wen

et al. 2003

Physica C: Superconductivity

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“…γ = 60 was obtained from angular resolved resistivity measurements using scaling arguments [27]. With κ 2 = λ ξ , B c2 = φ0 2πξ 2 , we find ξ (0) = 3.3nm, λ (0) = 2080nm consistent with the slightly overdoped regime [28]). The approximate field dependence of the critical current in a restricted field range is an indication but can not be taken as a proof of the validity of the model.…”

mentioning

confidence: 94%

On voltage-current characteristics and critical current in Bi-2212

Pautrat¹,

Simon²,

Scola³

et al. 2005

Eur. Phys. J. B

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V(I) characteristics have been performed in a monocrystalline microbridge of Bi[P b] − 2212. The vortex phase diagram has been greatly investigated. Linear but non-ohmic Voltage(Current) (V(I)) curves with well defined critical current have been observed. A departure from this behavior is observed near the peak effect where an out of equilibrium high threshold current can be stabilized. At high temperature, the critical current persists in the "liquid" state despite the dissipation at the lowest bias. Some implications of these results are discussed. In particular, it is proposed that the surface disorder, rather than the bulk disorder, is responsible for the vortex pinning in this sample. The generic vortex phase diagram in cuprates is now described in terms of into different thermodynamic phases of vortex [1]. The main idea is that an ordered Vortex Lattice (VL) is present at low field and low temperature, and that it develops into a phase possessing a degraded order when the thermal fluctuations or the static disorder are increased. This corresponds respectively to (ordered solid/liquid) and (ordered solid/disordered solid) transitions. The strong experimental facts which have justified these ideas are the disappearance of the vortex pinning in the "liquid" phase and the increase of this vortex pinning (the peak effect) when crossing the disordering transition. The highly anisotropic cuprate Bi-2212 can be taken as a representative sample where these three states can appear. Nevertheless, recent experiments suggest to qualify this point of view. Indeed, it has been found that both the high field and the high temperature properties can be interpreted with the same state of vortex matter, meaning that no difference between them should be presupposed [2,3]. Another striking result is that VL translational order is not a good order parameter to characterize the first order transition [4], whereas one could have expected the contrary for a genuine melting. From an experimental point of view, the VL behavior in Bi-2212 has been tackled at low field by magneto-optic imaging or local ac probes [2,3], which are sensitive to pinning induced screening currents on the surface of the samples. If the magnetic field is increased, the limited resolution of the above-cited experiments strongly restricts their ability to give information on the VL pinning and dynamical properties. One complementary and easily understandable experiment is the measure of a voltage versus current (V(I)) curve. The critical current I c , which gives the pinning ability of the medium, can be extracted without the need of complicated and possibly unjustified assumptions. Furthermore, it has been shown by numerous theories and simulations [5,6,7] that the nature of the VL

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“…It is known, that overdoping or underdoping of Bi 2 Sr 2 CaCu 2 O 8+δ can be achieved by cation substitutions or by changes in the oxygen content 41,42 . However, in the low-T c Bi-based phase Bi2201, we have found that it is difficult to change the number of holes, because it is difficult to change the oxygen content.…”

Section: Methodsmentioning

confidence: 99%

Metal-to-insulator crossover and pseudogap in single-layerBi2+xSr2−xCu1+<

Vedeneev

Maude

2004

Phys. Rev. B

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The in-plane ρ ab (H) and the out-of-plane ρc(H) magneto-transport in magnetic fields up to 28 T has been investigated in a series of high quality, single crystal, hole-doped La-free Bi2201 cuprates for a wide doping range and over a wide range of temperatures down to 40 mK. With decreasing hole concentration going from the overdoped (p=0.2) to the underdoped (p=0.12) regimes, a crossover from a metallic to and insulating behavior of ρ ab (T ) is observed in the low temperature normal state, resulting in a disorder induced metal insulator transition. In the zero temperature limit, the normal state ratio ρc(H)/ρ ab (H) of the heavily underdoped samples in pure Bi2201 shows an anisotropic 3D behavior, in striking contrast with that observed in La-doped Bi2201 and LSCO systems. Our data strongly support that that the negative out-of-plane magnetoresistance is largely governed by interlayer conduction of quasiparticles in the superconducting state, accompanied by a small contribution of normal state transport associated with the field dependent pseudogap. Both in the optimal and overdoped regimes, the semiconducting behavior of ρc(H) persists even for magnetic fields above the pseudogap closing field Hpg. The method suggested by Shibauchi et al. (Phys. Rev. Lett. 86, 5763, (2001)) for evaluating Hpg is unsuccessful for both under-and overdoped Bi2201 samples. Our findings suggest that the normal state pseudogap is not always a precursor of superconductivity.

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Doping dependence of the in-plane penetration depth and fishtail inBi2Sr2Ca

Cited by 32 publications

References 43 publications

Dimensional crossover of vortex dynamics induced by Gd substitution on Bi2212 single crystals

Dimensional crossover of vortex dynamics induced by Gd substitution on Bi2212 single crystals

On voltage-current characteristics and critical current in Bi-2212

Metal-to-insulator crossover and pseudogap in single-layerBi2+xSr2−xCu1+<

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