Effect of Cr atoms in vortex dynamics of NbSe2 superconductor and study of second magnetization peak effect

Abstract

We report on the high quality single crystal of CrxNbSe2 growth to study the effect of Cr impurity on the vortex dynamics of NbSe2 superconductor using M-H curves with different relaxation rates. The field dependence nature of critical current density (Jc) is well investigated using Larkin-Ovchinnikov collective pinning model and Anderson-Kim's plastic creep model. We have observed significant improvement in the field dependence nature of Jc with increasing Cr impurities in NbSe2. This reveals the crossover of vortex lattice from elastic (E) to plastic (P) creep region causing second magnetization peak (SMP) or fishtail effect at highest Cr concentration, which has not been yet observed. Also addition of Cr impurity enhances the Jc up to 4 × 105 A/cm2. However, the interaction between core region of vortices and pinning centres ensure the δl pinning in Cr0.0005NbSe2 and significantly improved with increment of Cr impurity, which allowing both δl and δTc mechanism. Both, δl and δTc core pinning strongly enhance the coupling between vortices in pinning potential of nonstatistical distribution of Cr impurity, which makes 3D magnetic fluxes into 2D nature. Furthermore, the point pining and surface pinning mechanisms are responsible for pinning at low magnetic field region in Cr0.0005NbSe2. The appearance of prominent peak in pinning force density near upper critical field (Hc2) indicates the lattice softening at higher Cr impurity. These studies not only provide fundamental study of vortex dynamic but also open the door for further study in low Tc superconducting materials. © 2018 IOP Publishing Ltd