Revelations of vortex phases and pinning mechanism in GdBa₂Cu₃O_7- superconductors: a magneto-electric and magnetization study

Rare earth (RE) and barium (Ba) based cuprate superconductors have garnered considerable attention in both fundamental research and a wide array of engineering and technological applications. Examining the impact of magnetic Gd3+ ions on the GdBa2Cu3O7-delta (GdBCO) system, this study reveals that the presence of Gd3+ ion has tilted the magnetic hysteresis loop, thereby affecting the critical current density (J(c)) at low temperatures. Through comprehensive magnetic and magneto-transport data analyses of the GdBCO sample, we have thoroughly explored the intricate behavior of vortices in response to magnetic fields and temperature variations, providing insight into the governing mechanism of vortex pinning. Remarkably, the absolute zero temperature pinning potential (U-0) experiences a significant reduction from a very high value of 3.18 eV to 0.45 eV with a magnetic field increase to 40 KOe, following a H-0.53 law, indicating 3D plastically crippled vortices in weak pinning sites due to point defects. In various technological domains, particularly those involving high temperatures and strong magnetic fields, understanding and optimizing the pinning force (F-p) and the pinning potential (U) of the vortices are pivotal for enhancing performance and efficiency. Consequently, we have meticulously analyzed the nature of F-p and U with the aid of the thermally activated flux flow (TAFF) model. Ultimately, we compiled a comprehensive phase diagram delineating the evolution of various vortex phases.