5 research outputs found
Peak effect in single crystal MgB superconductor for -axis
We have studied the phase diagram of MgB superconductor using a single
crystal for -axis. For the first time we report the
existence of peak effect in the screening current in MgB single crystal
for -axis. In the magnetic field regime kOe the
local fundamental diamagnetic moment displays a very narrow diamagnetic step,
with a temperature width of the same size as the zero dc-magnetic field
transition. For higher field this step is transformed to a peak which is
related with the peak effect in the screening current. Finally, for kOe
the diamagnetic step is transformed to a gradual transition. Our findings for
the vortex matter phase diagram for the MgB are closely related with
theoretical predictions concerning the vortex matter phase diagram of a type II
superconductor in the presence of weak point disorder.Comment: Has been submitted for publication in PRL since 21 February 200
Hysteretic behavior of the vortex lattice at the onset of the second peak for HgBaCuO superconductor
By means of local Hall probe ac and dc permeability measurements we
investigated the phase diagram of vortex matter for the HgBaCuO superconductor in the regime near the critical temperature. The second peak
line, , in contrast to what is usually assumed, doesn't terminate
at the critical temperature. Our local ac permeability measurements revealed
pronounced hysteretic behavior and thermomagnetic history effects near the
onset of the second peak, giving evidence for a phase transition of vortex
matter from an ordered qausilattice state to a disordered glass
Anomalous Peak Effect in CeRu2 and NbSe2 : Fracturing of a Flux Line Lattice?
CeRu2 and 2H-NbSe2 display remarkable similarities in their magnetic
response, reflecting the manner in which the weakly pinned flux line lattice
(FLL) loses spatial order in the Peak Effect (PE) regime. The discontinuous
change in screening response near the onset of PE and the history dependence in
it are attributed to a disorder-induced fracturing transition of the FLL, as an
alternative to the scenario involving the appearance of a spatial modulation in
superconducting order parameter in CeRu2.Comment: 4 pages of text and figures in ps for