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We present the vortex phase diagram for a single crystal of a low T c superconductor, Ca3Ir4Sn13 explored via detailed ac magnetic susceptibility (chi'(H,T)) and ac electrical resistivity (rho (H, T)) measurements. We observe a sharp peak effect (PE) phenomenon close to the superconducting-normal phase transition. This is in contrast to the findings for a second crystal of Ca3Ir4Sn13 in which a second magnetization peak was observed. Across the PE region, both the magnetization as well as the resistivity response depend on the thermomagnetic history of the sample. Further, the two measurement techniques (ac susceptibility and resistivity) reveal the occurrence of PE in different regions of the H-T phase space. In the high-field low-temperature region (H > 42 kOe and T < 3 K), the chi'(H,T) scans reveal a PE feature which is not observed in the rho (H, T) data. On the other hand, the rho (H, T) data display a sharp PE in the low-field high-temperature region (H < 23 kOe and T > 5 K) wherein the chi'(H,T) measurements do not show any signature of the PE. Two characteristic H-T regions have been identified in which only one of the two measurement techniques chi'(H,T) and rho (H, T)) assists to identify the PE boundary.

Serum beta-2 microglobulin and C-reactive protein levels were measured in 52 patients with acute adenovirus conjunctivitis and 58 healthy subjects, by ELISA technique. Serum beta-2 microglobulin levels were found to be significantly increased while there was no change in C-reactive protein levels. Serum beta-2 microglobulin levels closely paralleled the severity of the disease. The increased beta-2 microglobulin level in serum showed a significant fall to normal level on clinical improvement. There was no difference in the serum beta-2 microglobulin levels in virus-isolation positive and negative patients.

We report unusual jamming in driven ordered vortex flow in 2H-NbS2. Reinitiating movement in these jammed vortices with a higher driving force and halting it thereafter once again with a reduction in drive leads to a critical behavior centered around the depinning threshold via divergences in the lifetimes of transient states, validating the predictions of a recent simulation study Reichhardt and Olson Reichhardt, Phys. Rev. Lett. 103, 168301 (2009)] which also pointed out a correspondence between plastic depinning in vortex matter and the notion of random organization proposed Corte et al., Nat. Phys. 4, 420 (2008)] in the context of sheared colloids undergoing diffusive motion.

The driven state of a well-ordered flux line lattice in a single crystal of 2H-NbSe2 in the time domain has revealed the presence of substantial fluctuations in velocity, with large and distinct time periods (similar to seconds). A superposition of a periodic drive in the driven vortex lattice causes distinct changes in these fluctuations. We propose that prior to the onset of the peak effect there exists a heretofore unexplored regime of coherent dynamics, with unexpected behavior in velocity fluctuations.

We report observation of the de Haas-van Alphen oscillations in the mixed state as well as in the normal state of LuNi2B2C. Two oscillations alpha and eta are observed in the mixed state. In particular, the alpha oscillation can be studied not only deep in the mixed state as a function of magnetic field but also as a function of field direction. The damping rate of the oscillations due to superconductivity is found to be very anisotropic. For fields far below H-c2, the damping behavior is anomalous and cannot be explained only in terms of the superconducting gap. We argue that both the anisotropy of the gap and a disorder of the flux line lattice are responsible for the anisotropic and anomalous behavior of the damping in the mixed state.

The second magnetization peak and the peak effect anomaly coexisting in a given isothermal magnetization hysteresis loop show striking similarities in Ca3Rh4Sn13, a low-T-c superconductor and YBa2Cu3O7-delta, a high T-c superconductor. The observed variation of the hysteresis width with field could imply a modulation in the degree of the plastic deformation of the elastic vortex solid. The characteristics of the high-T-c cuprates, such as large Ginzburg number, short coherence length, decoupling of the Josephson coupled pancake vortices, etc., are unlikely to be the cause of the observed behavior.

The magnetic field dependence of the critical current is studied in single-crystal samples of the weak pinning type-II superconductor 2H-NbSe2 in the high-temperature and the low-field region of the (H,T) space. The experimental results demonstrate various pinning regimes: a collective pinned quasiordered solid in the intermediate-field range that is destabilized in favor of disordered vortex phases in both high fields near H-c2 and at low fields near H-c1. The temperature evolution of the pinning behavior demonstrates how the amorphous limit (where the correlation volume is nearly field independent) is approached around the so-called nose region of the reentrant peak-effect boundary. In the high-field regime the rapid approach to the amorphous limit naturally yields a peak effect, i.e., a peak in the critical current. In the low-field regime the crossover to the individual pinning regime gives rise to a "plateau effect." We show that with increasing effective pinning the peak effect shifts away from H-c2 and resembles a "fishtail" anomaly.

The peak effect (PE) region in a single crystal of Ca3Rh4Sn13 is shown to comprise two discontinuous first-order-like transitions located near its onset and peak positions, in accordance with a stepwise fracturing of the flux-line lattice. Magnetization response to thermal cycling across the onset position produces an open hysteresis loop, consistent with the notion of the fracturing. A thermomagnetic history dependence study shows that the critical current density J(c)(H,T) is path dependent over a large part of the (H,T) parameter space. Tills path dependence ceases above the peak position of the peak effect, suggesting a complete amorphization of the flux-line lattice at (T-p,H-p) line. A plausible vortex phase diagram has been constructed for Ca3Rh4Sn13 in which phases like an elastic solid, a plastic solid, and pinned and unpinned amorphous states have been identified.

The phenomenon of superconductivity was discovered in 1911, however, the methodology to classify and distinguish type-IT superconductivity was established only in late fifties after Abrikosov's prediction of a flux line lattice in 1957. The advent of high temperature superconductors (HTSC) in 1986 focused attention onto identifying and classifying other possible phases of vortex matter in all classes of superconductors by a variety of techniques. We have collated evidences in support of a proposal to construct a generic phase diagram for weakly pinned superconducting systems, based on their responses to ac and de magnetic fields. The phase diagram comprises quasi-glassy phases, like, the Bragg glass, a vortex glass and a reentrant glass in addition to the (completely) amorphous phases of pinned and unpinned variety. The characteristic metastability and thermomagnetic history dependent features recognized amongst various glassy vortex phases suggest close connections between vortex matter and other disordered condensed matter systems, like, spin glasses, super cooled liquids/ structural glasses, etc. A novel quenched random disorder driven fracturing transition stands out amongst other noteworthy facets of weakly vortex pinned vortex matter.

The magnetic field dependent r.f. (20 MHz) power dissipation, P(H) vs H, for H-r.f. \\ c \\ H in Bi2Sr2CaCu2O8 (Bi 2 2 1 2) Single crystals shows an onset at T similar to 102 K, nearly 20 K above the nominal T-C (similar to 82 K). In contrast, for H-r.f. \\ ab, H \\ c, the onset of losses occurs at the T-C. One possible reason for the onset at similar to 102 K could be the Bi2Sr2Ca2Cu3O8 (Bi 2 2 2 3) inclusions with a T-C similar to 100-110 K. However, our non-resonant r.f. absorption studies cast doubt on this conclusion and point towards an alternative explanation in terms of superconducting fluctuations above the T-C of Bi 2 2 1 2 single crystals. Support for this is provided by the characteristic temperature dependence of the magnetic field dependent r.f. dissipation.

The results of nonresonant microwave absorption (NRMA) studies in Bi2212 single crystals for the $H\Vert c$ axis and $H\Vert ab$ plane are reported. In the former orientation, over a few degrees below $T_c$ , the NRMA signal shapes evolve continuously as a function of temperature. We interpret these results as indicative of rapid strengthening of Josephson coupling between the pancake vortices in the $CuO_2$ bilayers on cooling below $T_c$ . For $H\Vert ab$ there is almost no change in the signal shape in the temperature range studied. In this case, no loss component attributable to Josephson coupling is observed.

The response of the vortices in a dynamic state is studied in single crystals of Bi2212 using the technique of non-resonant microwave absorption (NRMA). It is observed that with the magnetic field (H) normal to the $CuO_2$ planes, the NRMA signal has two components-a low-field narrow derivative and a broad high-field signal. We study their orientational dependence and observe a sudden increase in the low-field dissipation as the field becomes nearly parallel to $CuO_2$ planes. We interpret it as a signature of lock-in-transition

We have studied the magnetic field dependent non-resonant rf losses in as-grown Bi2212 single crystals prior to and after irradiation with 250 MeV $^{107}Ag^{17+}$ ions. In the pristine state the losses from the inter-unit cell and intra-unit cell weak links are identified. The interesting feature is that the losses from inter-unit cell weak links reappear as the columnar tracks age with time suggesting that temperature cycling and thermal effects have important consequences on the robustness of the tracks. The losses from the intra-unit cell weak links although suppressed after irradiation, disappear suddenly at a certain temperature below Tc. This is unlike in the pristine state where the losses decrease smoothly as the temperature is decreased

The irreversibility line for H?c in a single crystal specimen of Bi2Sr2CaCu2O8+? (Bi2212) has been determined via vanishing of hysteresis in isothermal dc magnetization measurements. The hysteresis loops (H?c) in Bi2212 appear to show signatures of two-component magnetic response in several temperature regions where the temperature dependence of irreversibility field charges sharply. It is proposed that the observed behavior may be a consequence of existence of weak links of varying strength in Bi2212