LAUSR

We report the studies of detailed magnetic relaxation and isothermal magnetization measurements in the vortex state of the 112-type iron-pnictide Ca0.82La0.18Fe0.96Ni0.04As2 superconductor with Tc∼ 22 K. In the isothermal M(H), a well defined second magnetization peak (SMP) feature is observed in the entire temperature range below T c for measurements with H∥c -axis. However, for H∥ab -planes, the SMP feature is suppressed at low temperatures, which might be due to 2D Josephson vortices forming at low temperatures and high magnetic fields in such an anisotropic system. A rigorous analysis considering the magnetic relaxation data for H∥c -axis suggests an elastic to plastic pinning crossover across H p , which also seems accompanied with a possible phase transition in vortex lattice near Hp . Moreover, point disorder and surface defects are likely to be the dominant sources of pinning, which contribute to the δl -type of pinning in the sample. A high J c , in access of 105 A cm−2 observed could potentially make this material technologically important.