SHIELDING CURRENTS AND CURRENT-VOLTAGE CHARACTERISTICS OF BI2SR2CA1CU2O8-CRYSTAL(DELTA SINGLE)

The dependence of the irreversible magnetization on the external magne tic field sweep rate, dH(e)/dt, and its time relaxation are studied in a Bi2+xSr2+yCa1+zCu2O8+delta (x = 0.11, y = 0.12, z = -0.25) single c rystal. Two characteristic regions are found with a transition tempera ture T between 15 and 20 K depending on dH(e)/dt and relaxation time. Below T the magnetic field dependence of the shielding currents foll ows a scaling law J(s)(H(e),T)/J(s)(0,T)=f[H(e)/J(s)(0,T)] with a univ ersal 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 approximately 1/T. Above T a deviation from the J(s)(H(e)) scaling behavior and a transition to m uch steeper voltage current characteristics are observed. Possible rea sons of these different shielding current behaviours are discussed.