Irreversibility temperatures in superconducting oxides: The flux-line-lattice melting, the glass-liquid transition, or the depinning temperatures

Abstract

The magnetic-field dependence of the irreversibility temperatures follows an H=a[1-Tr(H)/Tc(0)]n relationship with n≃1.5, for pure and alloyed YBa2(Cu1−xMx)3O7+δ with x=0 and 0.02, where M=Al, Fe, Ni, and Zn, measured for an applied field parallel to the c axis. However, for M=Ni and x=0.04 and 0.06, n≃2.0. This relationship is not applicable for either Bi2Sr2CaCu2O8 or (Bi,Pb)2Sr2Ca2Cu3O10 powders. It is also shown that the irreversibility temperature is a strong function of the magnetic hysteresis width ΔM for pure and alloyed YBa2Cu3O7. These results and the measurements of the flux creep ΔM(t) for these specimens suggest that Tr(H) is a depinning line rather than a lattice melting or glass-to-liquid phase-transition temperature. However, the conventional flux-creep model cannot account for all of the observed temporal dependences of ΔM(t).

Source-reported materials — not catalogue approval

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