Anisotropy in the vortex phase diagram and the pinning force density in the basal plane of YNi2B2C

We present the magnetic field dependence of the critical current density from dc magnetization measurements concerning the anisotropic behaviour of flux line lattice (FLL) in a single crystal of YNi2B2C. The peak effect (PE) phenomenon is observed for all crystallographic orientations, but the second magnetization peak (SMP) anomaly is observed only for H-parallel a. Our study reveals that the FLL obtained when H-parallel [110] is better ordered within the basal plane. However, the FLL for H-parallel c is found to be even more ordered than that for H-parallel [110]. The perfect square symmetry of the FLL for H-parallel c is perhaps responsible for promoting the realization of the best spatial order of the FLL prior to the onset of the PE, indicating a correlation between the crystalline lattice and the vortex lattice. We have also found a change over in the power law governing the decay of the critical current density which is identified as a crossover from weak to weaker pinning regime in the phase diagram