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_{1y}Se." Journal of Low Temperature Physics 179, no. 12 (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 pinningrelated feature at TeX 57 TeX off the plane while the pure TeX FeSe phase samples show the persistence of a strong angulardependent magnetoresistance characteristic of the normal state electronic structure.


D'Anna, G., and Andr. "Fluxline response in 2HNbSe2 investigated by means of the vibrating superconductor method." Physica C: Superconductivity and its applications 218, no. 12 (1993): 238–244.
Abstract: We measure transverse AC losses in the low and highamplitude regime of 2HNbSe2 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 HT phase diagram the “peakeffect” line which is supposed to mark an abrupt crossover in the vortexpinning regime.


Herbsommer, J. A., J. Luzuriaga, L. Civale, G. Nieva, G. Pasquini, H. Lanza, and P. Levy. "Angular variation of pinning near the irreversibility temperature in single crystal Y Ba2Cu3O7? with splayed columnar defects." Physica C 304, no. 12 (1998): 112–118.
Abstract: We have studied vortex pinning through ac susceptibility measurements in single crystals of YBCO with columnar defects (CDs). The CDs have 0, 10 and 20 splay angle and average direction 108 off the caxis. By studying the angular variation we can compensate for the anisotropy and effects of twins, etc. Using a simple expression we can obtain the angular spread when the field direction is outside the splay angle. An increase of pinning when the field direction is inside
the angle defined by the CDs can be attributed to vortex entanglement due to the splay and the suppression of the sliding of double kinks.


L. "Dynamic softening of vortex lines in YBa2Cu3O7? single crystals." Physica C: Superconductivity and its Applications 260, no. 34 (1996): 211–216.
Abstract: Transport measurements in the mixed state of oxygendeficient YBa2Cu3O7? single crystals using the flux transformer configuration show that the flux liquid changes with increasing anisotropy from strongly correlated to uncorrelated in the field direction. For intermediate coupling, the current inducing loss of vortex correlation has a maximum near the irreversibility temperature. Thus, an effective softening of vortex lines with decreasing temperature is detected. We propose a simple model that accounts for this behavior by including the effects of the pinning potential on the dynamics of vortices.

