Flux-line response in 2H-NbSe2 investigated by means of the vibrating superconductor method

Dimensionality of collective pinning in2H−NbSe2single crystals

“…This linear dependence has been previously reported by D'Anna et al 14 If we combine this behavior with the fact that h peak (T) is constant, a linear relation between H c2 and the temperature should be expected and the slope of this line should be Ϫ 0 (dH c2 /dT)ϭ0.786 T/K. This value is very close to the values reported from magnetization measurements in the initial studies performed on 2H-NbSe 2 using a similar geometry.…”

“…13 In the high-field regime, however, a peak effect ͑PE͒ occurs in J c (H dc ) or J c (T) close to the critical field line H c2 (T). 11,14,15 Different scenarios have been suggested for the PE: ͑i͒ a sudden softening of the elastic moduli on going from local to nonlocal elasticity, 13 ͑ii͒ a dimensional crossover from two-dimensional ͑2D͒ to 3D collective pinning, 11 ͑iii͒ a melting transition of the vortex lattice at the onset of the peak, 16 or ͑iv͒ at the maximum of the PE. 17,18 In this paper we are not considering the origin of the PE, but we concentrate on the dimensionality of the collective pinning in the field regime below the PE, which is nonetheless relevant for ͑i͒ and ͑ii͒.…”

Disordering of the vortex lattice through successive destruction of positional and orientational order in a weakly pinned Co0.0075NbSe2 single crystal

“…These studies rely on the fact that in the presence of random pinning centres, the VL gets more strongly pinned to the crystal lattice as the perfect hexagonal order of the VL is relaxed 28 . The order-disorder transition thus manifests as sudden non-monotonic enhancement of bulk pinning 29 , and consequently of the critical current and the diamagnetic response in ac susceptibility measurements. Known as the “peak effect”, this has been a central theme of many studies on the static and dynamic properties of VLs.…”

Orientational coupling between the vortex lattice and the crystalline lattice in a weakly pinned Co0.0075NbSe2single crystal

“…These TD relax the hexagonal order which make it easier for vortices to accommodate the random pinning potential thereby enhancing the effective pinning. Thus the ODT manifests as a sharp increase in the critical current or a decrease in the real part of ac susceptibility (χ′), the so called 'peak effect' [9], which has been widely studied in weakly pinned superconducting crystals [1,10].…”