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It is commonly accepted that the peak effect (PE) in the critical current density of type II superconductors is a consequence of an order-disorder transition in the vortex lattice (VL). Examination of vortex lattice configurations (VLCs) in its vicinity requires the use of experimental techniques that exclude current induced VL reorganization. By means of linear ac susceptibility experiments in the Campbell regime, where vortices are forced to oscillate (harmonically) around their effective pinning potentials, we explore quasi-static stable and metastable VLCs in NbSe_{2} single crystals near the PE. We identify three different regions: for T<T_{1}(H), stable VLCs are maximally ordered. For T>T_{2}(H) configurations are fully disordered and no metastability is observed. In the T_{1}<T<T_{2} region we find temperature dependent stable configurations with intermediate degree of disorder, possibly associated to coexistence of ordered and disordered lattices throughout the PE. A simple estimation of the equilibrium proportion of ordered and disordered domains is provided.
Particles occupying sites of a random lattice present density fluctuations at all length scales. It has been proposed that increasing interparticle interactions reduces long range density fluctuations, deviating from random behaviour. This leads to p
We report structural evidence of dynamic reorganization in vortex matter in clean NbSe$_2$ by joint small angle neutron scattering and ac-susceptibility measurements. The application of oscillatory forces in a transitional region near the order-disor
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