Flux jumps, Second Magnetization Peak anomaly and the Peak Effect phenomenon in single crystals of $YNi_2B_2C$ and $LuNi_2B_2C$

TL;DR

This study investigates flux jumps, the second magnetization peak, and the peak effect in single crystals of YNi2B2C and LuNi2B2C, revealing flux jumps linked to structural flux line lattice transitions and differences in vortex phase diagrams due to sample purity.

Contribution

It provides new insights into flux lattice re-orientation transitions and compares vortex phase diagrams in two related superconductors, highlighting the impact of sample purity.

Findings

Flux jumps relate to local symmetry changes in flux line lattice.

Flux jumps occur at different fields in YNi2B2C and LuNi2B2C.

Ordered elastic glass phase is larger in LuNi2B2C, indicating higher purity.

Abstract

We present magnetization measurements in single crystals of the tetragonal $YNi_2B_2C$ compound, which exhibit the phenomenon of peak effect as well as the second magnetization peak anomaly for H $>$ 0.5T (H $||$ c). At the lower field (50mT $<$ H $<$ 200mT), we have observed the presence of flux jumps, which seem to relate to a structural change in the local symmetry of the flux line lattice (a first order re-orientation transition across a local field in some parts of the sample, in the range of 100mT to 150mT). These flux jumps are also observed in a single crystal of $LuNi_2B_2C$ for H $||$ c in the field region from 2 mT to 25 mT, which are compatible with the occurrence of a re-orientation transition at a lower field in a cleaner crystal of this compound, as compared to those of $YNi_2B_2C$. Vortex phase diagrams drawn for H $||$ c in $LuNi_2B_2C$ and $YNi_2B_2C$ show that the ordered elastic glass phase spans a larger part of (H, T) space in the former as compared to latter, thereby, reaffirming the difference in the relative purity of the two samples.