Critical current density and flux pinning in an unconventional superconductor

The functional dependence of the critical current density on magnetic field, Jc(H), observed at fixed temperatures in the unconventional type-II superconductor, LaAg1−cMnc (c=0.1,0.2,0.3) alloys, but not the relative magnitude of Jc in different alloy compositions at any given temperature and field, is adequately described by the exponential-decay critical state model. In accordance with the predictions of the Kramer's flux-pinning model, the peak value of the pinning force density FPmax∝(Hc2)m with the exponent 1.7⩽m⩽2.8 and FP/FPmax scales with h=H/Hc2, where Hc2 is the upper critical field. Irrespective of sample composition and temperature in the superconducting state, the pinning of the flux line lattice (FLL) dominates over the plastic FLL shear.