New Features in the Vortex Phase Diagram ofYBa2Cu3O7−δ

Abstract

Magnetic and transport measurements have been performed in high quality YBa 2 Cu 3 O 72d single crystals. We demonstrate for the first time that the magnetization peak line in the phase diagram of YBa 2 Cu 3 O 72d , H p ͑T͒ exhibits an impressive similarity with the equivalent line for Bi 2 Sr 2 CaCu 2 O 8 . Our results show not only a similar temperature dependence but also an almost identical response to oxygen doping and a correlation to the multicritical point. At high temperatures we observe a previously unreported splitting of the magnetization peak. [S0031-9007(97)

Critical points in the Bragg glass phase of a weakly pinned crystal of Ca3Rh4Sn13

“…The field values of this SMP anomaly do not appear to vary with temperature. Prior to such a result in Ca 3 Rh 4 Sn 13 , the SMP anomaly located deeper inside the mixed phase, which is distinct from the PE anomaly could be noted in the data of some of the crystals of high T c YBa 2 Cu 3 O 7 compound [14,15,16,17], however, the loci of SMP/PE fields in these samples have very different (complex and non-monotonic) behavior. Subsequent investigations in some of the weakly pinned crystals of 2H-NbSe 2 , LuNi 2 B 2 C, YNi 2 B 2 C, etc., have also revealed the presence of a tiny SMP anomaly distinct from the PE in isothermal magnetization hysteresis scans [18,19,20].…”

SANS study of vortex lattice structural transition in optimally doped (Ba1−xKx)Fe2As2

“…Below 30 K, strong pinning dominates, and no SMP is observable. At higher temperatures, the central peak gives way to collective pinning by atomic-sized point defects [8] and to the increase of the magnetic moment (SMP) at the onset field B OD [12,11,4,8], the temperature dependence of which is shown in Fig. 4d.…”

“…Upon heating, the ordered vortex solid transits to the vortex liquid. However, an increase in vortex density at low temperature is also followed by a first order transition, to a second vortex solid (or glassy) phase with strongly modified dynamics [4,10,11,12,6]. The change in current-voltage characteristics that this entails leads to the so-called "second magnetization peak" (SMP) phenomenon in numerous type II superconductors.…”

“…4d), suggesting that it corresponds to an intrinsic "order-disorder" transition of the vortex ensemble Refs. [1,12,11,42,4,6].…”

“…The change in current-voltage characteristics that this entails leads to the so-called "second magnetization peak" (SMP) phenomenon in numerous type II superconductors. The first order transition at the SMP onset field, B sp [12,11], has been interpreted either in terms of a structural change from a dislocation-free vortex "Bragg glass" to a plastically disordered phase [13,14,15], or in terms of the loss of vortex integrity along the field direction [6,16]. Thus, the understanding of the vortex phase diagram in disordered superconductors is incomplete at best, unsettled questions being the mechanism of the SMP transition, the link between vortex solid structure and dynamics, the nature of the vortex glass, and whether the high-field vortex solid is, in all cases, distinct from the liquid.…”