Manifestation of modulation in spatial order of flux line lattice in weakly pinned superconductors : a vibrating sample magnetometer study

摘要

We have investigated the healing of transient disordered vortex statesinjected into a superconducting sample during the field ramping process inisothermal M-H measurements as a prescription to comprehend the modulation inthe state of order of the underlying equilibrium vortex state in weakly pinnedsingle crystals of $2H$-NbSe$_2$ (zero field transition temperature, $T_c(0)\sim 6 K$) and Ca$_3$Rh$_4$Sn$_{13}$ ($T_c(0) \sim 8.2 K$), which displayorder-disorder transition(s). Our results reaffirm the notion that spatialorder in the flux line lattice proceeds to the amorphous state in two distinctsteps as evidenced by the presence of second magnetization peak (SMP) anomalyand the peak effect (PE) phenomenon. Disordering commencing at the onset fieldof SMP has a window to heal between its peak field ($H_{smp}^p$) and the onsetfield ($H_p^{on}$) of the PE. A comparison of the scan rate dependence ofmagnetization hysteresis widths in two different crystals of $2H$-NbSe$_2$, oneof which displays only the PE phenomenon and the other one that displays bothSMP and PE anomalies, show that while enhancment in quenched random pinninginvokes the occurence of SMP anomaly, it slows down the temporal decay ofcurrents across the PE region.