Stepwise amorphization of the flux-line lattice in Ca₃Rh₄Sn₁₃: a peak-effect study

Abstract

The peak effect (PE) region in a single crystal of Ca₃Rh₄Sn₁₃ is shown to comprise two discontinuous first-order-like transitions located near its onset and peak positions, in accordance with a stepwise fracturing of the flux-line lattice. Magnetization response to thermal cycling across the onset position produces an open hysteresis loop, consistent with the notion of the fracturing. A thermomagnetic history dependence study shows that the critical current density J_c(H,T) is path dependent over a large part of the (H,T) parameter space. This path dependence ceases above the peak position of the peak effect, suggesting a complete amorphization of the flux-line lattice at (T_p,H_p) line. A plausible vortex phase diagram has been constructed for Ca₃Rh₄Sn₁₃ in which phases like an elastic solid, a plastic solid, and pinned and unpinned amorphous states have been identified.