Magnetic hysteresis studies of Tl-2223 substituted by Fe and Zn

Effect of Fe and Zn substitutions on the magnetic hysteresis of Tl-2223 are investigated in high magnetic fields up to 9 Tesla and at different temperatures (T= 6, 20, 40 and 80 K). The results of magnetic hysteresis loops show that the area of these loops decreases as Fe-content increases, whereas it increases for Zn-substitutions till x = 0.2 and then decreases for x $>$ 0.2. The magnetization difference $\Delta $M is found to decay exponentially with temperature at low magnetic fields, according to $\Delta $M $\alpha $ exp (-T/T$_{0})$. The characteristic temperature T$_{0}$ is found to be varied from 6 K to 40 K and it is related to the applied magnetic field B according to T$_{0} \quad \alpha $ B$^{-1/n}$. The critical current density is calculated for the prepared samples from magnetic hysteresis measurements and compared with that determined from ac magnetic susceptibility. The results are discussed according to the flux motion and flux pinning.