Origin of experimental order-disorder transition line curvature in the La2-x Srx CuO4 single crystal vortex system at low temperatures

We investigated the dc magnetization curves of overdoped La2-x Srx CuO4 single crystals in the low-temperature T range, with the external magnetic field H oriented along the c axis. It was found that the onset field for the second magnetization peak, associated with the order-disorder transition in the vortex system, increases significantly with decreasing T in the low- T region, where the superconductor parameters are independent of T. The upward curvature of the order-disorder transition line determined in standard magnetization measurements at low T is explained by considering the reduction of the actual pinning energy due to the macroscopic currents induced in the sample. A simple energy balance equation for the dynamic conditions generated in the widely performed magnetization studies is proposed.