Effects of Lu Doping on the Magnetic Behavior of YBCO Superconductors Prepared by MPMG Method

We report on magnetic behavior of Y _1?xLu _xBa ₂ Ca ₃ O _7?δ (x= 0, 0.5) samples synthesized by a modified melt powder melt growth (MPMG) method at three different sintering temperatures (920, 930, 940 ^°C). Isothermal magnetization measurements were done as a function of magnetic field at 20 and 77 K upon zero-field cooling (ZFC) process. The critical current densities as a function of magnetic field have been estimated from M–H hysteresis loop. Partial Lu substitution for Y on YBCO superconductors improved significantly the bulk critical current density, which is confirmed by field-cooled magnetization and AC susceptibility measurements. Magnetic relaxation measurement has been carried out in remanent magnetization regime. AC susceptibility measurements have been performed as a function of temperature to determine the transition temperature.