Shielding currents and current-voltage characteristics of Bi2Sr2Ca1Cu2O8+δ single crystal

Abstract The dependence of the irreversible magnetization on the external magnetic field sweep rate, d H e /d t , and its time relaxation are studied in a Bi 2+ x Sr 2+ y Ca 1+ z Cu 2 O 8+δ ( x =0.11, y =0.12, z =-0.25) single crystal. Two characteristic regions are found with a transition temperature T ∗ between 15 and 20 K depending on d H e /d t and relaxation time. Below T ∗ the magnetic field dependence of the shielding currents follows a scaling law J s ( H e , T )/ J s (0, T )= f [ H e / J s (0,T)] with a universal function f independent of temperature and sweep rate of magnetic field. Voltage-current characteristics are described quite well by a power-like law E / E c =( J s / J c ) n with n ∼1/ T . Above T ∗ a deviation from the J s ( H e ) scaling behavior and a transition to much steeper voltage-current characteristics are observed. Possible reasons of these different shielding current behaviours are discussed.