Peak effects and the solid vortex phase of a T*-phase SmLa0.8Sr0.2CuO4-delta single crystal - art. no. 134502

The isothermal magnetization curves obtained from a superconducting T*-phas e SmLa0.8Sr0.2CuO4-delta single crystal have demonstrated the existence of distinct peak effect in a large temperature range, persisting up to the vic inity of the superconducting critical temperature (T(c)(on)approximate to 2 4 K). The magnetization curves also exhibit the remarkable feature of zero- field peaking and its enhancement at lower temperature. Analysis of the ass ociated vortex phase diagram further establishes the role of geometrical ba rrier in the retardation of vortex penetration at high temperature and that of surface barrier at lower temperature. The temperature dependence of the second peak field is also found to conform with existing models at the app ropriate temperature regimes. Additionally, the irreversibility line shows a sign reversal of its slope at a field position around H-2D indicating two -dimensional melting at higher field. Nevertheless, the temperature depende nt behavior of the second peak onset field is at variance with other publis hed results and defies explanation on the basis of existing theoretical mod els.