Analysis of Magnetic Properties and Critical Current Density of Tl-2234 High-Temperature Superconductor Using AC Magnetic Susceptibility Measurements

This study investigates the magnetic properties and critical current density of Tl₂Ba₂Ca₃Cu₄O₁₁₊δ (Tl-2234) high-temperature superconductors through AC magnetic susceptibility measurements. Samples were synthesized using a one-step solid-state process with careful heat treatment protocols to minimize thallium evaporation. AC susceptibility measurements were conducted across temperatures ranging from 140 to 50K under various applied AC magnetic fields (0.5-8 mT). The analysis revealed a sharp transition primarily reflecting intragranular superconductivity, with the field dependence of the imaginary (χ'') component providing insights into flux dynamics within the grains. The imaginary component peaks shifted towards lower temperatures with increasing magnetic field strength, indicating enhanced magnetic field penetration and increased intra-grain pinning centers. Using Bean's critical-state model, with an estimated effective particle radius of R ≈ 44.5 µm based on sieve size, the critical current density (Jc) was calculated from the peak positions in χ''(T) curves. The temperature dependence of Jc followed an empirical scaling relation, yielding a zero-temperature critical current density Jc(0) of 3.6×10⁵ A/cm² and a critical exponent of 1.26 ± 0.08, quantifying key superconducting parameters of the prepared material