Alex Grover

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Ž . The disordering of a flux line lattice FLL is studied in weak pinning single crystal samples of the layered low-Tc superconductor NbSe containing varying amounts of quenched disorder. The phenomenon of the peak effect, i.e., an 2 anomalous peak in the critical current, attributed to a collapse of the correlated volume of the pinned FLL, shows a rich Ž .(More)
A reentrant peak effect is observed through low field ac susceptibility measurements on the weakly pinned flux line lattice in single crystals of 2H-NbSe2. The resulting phase diagram of the peak effect is strikingly similar to the theoretically predicted reentrant phase boundary which separates flux lattice and flux liquid phases. The broadening and(More)
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 ( approximately seconds). A superposition of a periodic drive in the driven vortex lattice causes distinct changes in these fluctuations. We propose(More)
We present the evolution of novel phenomena of magnetic compensation effect, exchange bias (EB) effect and the field induced anomalies in '[Formula: see text]' substituted multiferroic compound [Formula: see text]. A few percent of '[Formula: see text]' substitution for '[Formula: see text]' in [Formula: see text] results in the reversal of field cooled(More)
We present magnetization data on a weakly pinned CeRu2 single crystal showing the existence of a stable state of the vortex lattice in the peak effect region. The stable state is achieved by cycling the magnetic field by small amplitude. This stable state is characterized by a unique value of critical current density (Jc), independent of the magnetic(More)
Under the influence of a constant drive the moving vortex state in 2H-NbS2 superconductor exhibits a negative differential resistance (NDR) transition from a steady flow to an immobile state. This state possesses a high depinning current threshold ([Formula: see text]) with unconventional depinning characteristics. At currents well above [Formula: see(More)
A comparison of the history effects in weakly pinned single crystals of a high Tc YBa2Cu3O7−δ (for H ‖ c) and a low Tc Ca3Rh4Sn13, which show anomalous variations in critical current density Jc(H) are presented via tracings of the minor magnetization hysteresis loops using a vibrating sample magnetometer. The sample histories focussed are, (i) the field(More)
X iv :c on dm at /9 90 82 22 v1 [ co nd -m at .s up rco n] 1 6 A ug 1 99 9 A study of supercooling of the disordered vortex phase via minor hysteresis loops in 2H-NbSe2 G. Ravikumar, P. K. Mishra, V. C. Sahni, S. S. Banerjee, A. K. Grover, S. Ramakrishnan, P. L. Gammel, D. J. Bishop, E. Bucher, M. J. Higgins and S. Bhattacharya TPPED, Bhabha Atomic Research(More)
A universal phase diagram for weakly pinned low-Tc type-II superconductors is revisited and extended with new proposals. The low-temperature “Bragg glass” phase is argued to transform first into a disordered, glassy phase upon heating. This glassy phase, a continuation of the high-field equilibrium vortex glass phase, then melts at higher temperatures into(More)