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D'Anna, G., and Andr. "Flux-line response in 2H-NbSe2 investigated by means of the vibrating superconductor method." Physica C: Superconductivity and its applications 218, no. 1-2 (1993): 238–244.
Abstract: We measure transverse AC losses in the low- and high-amplitude regime of 2H-NbSe2 single crystals using vibrating superconductor methods. The measurements are sensitive to small deviations of the critical state. The data constitute evidence for a peak effect of the critical current as a function of the temperature in this compound. We construct in the H-T phase diagram the “peak-effect” line which is supposed to mark an abrupt cross-over in the vortex-pinning regime.
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Kim, J., N. Haberkorn, E. Nazaretski, R. de Paula, T. Tan, X. X. Xi, T. Tajima, R. Movshovich, and L. Civale. "Strong magnetic field dependence of critical current densities and vortex activation energies in an anisotropic clean MgB2 thin film." Solid State Communications 204 (2015): 56–60.
Abstract: We report the influence of two-band superconductivity on the flux creep and the critical current densities of a MgB2 thin film. The small magnetic penetration depth of λ=50±10 nm at T=4 K is related to a clean π-band. We find a high self-field critical current density Jc, which is strongly reduced with applied magnetic field, and attribute this to suppression of the superconductivity in the π-band. The temperature dependence of the creep rate S (T) at low magnetic field can be explained by a simple Anderson–Kim mechanism. The system shows high pinning energies at low field that are strongly suppressed by high field.
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Kim, J., N. Haberkorn, K. Gofryk, M. J. Graf, F. Ronning, A. S. Sefat, R. Movshovich, and L. Civale. "Superconducting properties in heavily overdoped Ba(Fe0.86Co0.14)2As2 single crystals." Solid State Communications 201 (2015): 20–24.
Abstract: Abstract
We report the intrinsic superconducting parameters in a heavily overdoped Ba(Fe1−xCox)2As2 (x=0.14) single crystal and their influence in the resulting vortex dynamics. We find a bulk superconducting critical temperature of 9.8 K, magnetic penetration depth λab (0)=660±50 nm, coherence length ξab (0)=6.4±0.2 nm, and the upper critical field anisotropy γT→Tc≈3.7. The vortex phase diagram, in comparison with the optimally doped compound, presents a narrow collective creep regime. The intrinsic pinning energy plays an important role in the resulting vortex dynamics as compared with similar pinning landscape and comparable intrinsic thermal fluctuations.
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Amigó, M. L., M. V. Ale Crivillero, D. G. Franco, J. Guimpel, and G. Nieva. "Influence of the Fe Concentration on the Superconducting Properties of Fe_{1-y}Se." Journal of Low Temperature Physics 179, no. 1-2 (2015): 15–20.
Abstract: We present a comparative study of electrical transport properties in the normal state and in the dissipative superconducting state between pure TeX -FeSe phase and Fe deficient Fe TeX Se crystals. We discuss the influence of the intergrowth of the magnetic hexagonal phase (Fe TeX Se TeX ) in Fe deficient samples when compared to pure TeX -FeSe samples. In the superconducting state, we measured the TeX -plane electrical resistivity with magnetic field up to 16 T and the electrical resistivity as a function of the angle between the TeX axis and the applied field. The angular dependence at fixed temperature below the superconducting critical temperature, TeX , is very different for both sets of crystals. The Fe deficient samples display a vortex pinning-related feature at TeX 57 TeX off the plane while the pure TeX -FeSe phase samples show the persistence of a strong angular-dependent magnetoresistance characteristic of the normal state electronic structure.
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