Rectifying the second magnetization peaks. Comments on “Revealing the vortex phases and second magnetization peaks in SmBCO superconductors

https://doi.org/10.1063/5.0235000

Rare earth substitution in cuprate superconductors has sparked intense interest, driving progress in both fundamental research and advanced technology. In this investigation, we focus on SmBa 2Cu 3O 7−� (SmBCO), synthesized via the top-seeded melt growth method, with an aim to understand the corresponding vortex phases. Despite the minimal impact on transition temperature (⁠ ��⁠) when yttrium in YBa 2Cu 3O 7−� is replaced by Sm, the critical current density (⁠ ��⁠) remains exceptionally high under intense magnetic fields. Introducing Sm 2Ba 1Cu 1O 5 (Sm-211) phase as point defects significantly boosts the pinning potential (⁠ �⁠) and pinning force (⁠ ��⁠) and enhances their stability against external magnetic fields. Contrary to other superconductors, the SmBCO sample displays a notable peak effect in the magnetic field-dependent ��⁠, driven by point defects introduced by the Sm-211 phase, which prompts vortex lattice softening and initiates a transition from an ordered to a disordered vortex glass phase, leading to the emergence of a second magnetization peak. Analysis suggests that the primary pinning mechanism in SmBCO involves a combination of normal point and Δ� pinning. Additionally, investigations of the vortex glass phase beneath the thermally activated flux flow regime indicate that vortices in SmBCO may freeze into a state akin to a 2D vortex glass state. This study leads to a detailed phase diagram that clarifies the evolution of vortex phases in SmBCO.