Effective activation energy in the Bi-Sr-Ca-Cu-O systems

Magnetic relaxation in the Bi-Sr-Ca-Cu-O systems was investigated over a wide temperature regime. Previously reported studies of the effective activation energy, U, have been controversial in terms of temperature and field dependence of the critical current density, j/sub c/. The authors considered the temperature dependence of j/sub c/ and constructed the U-j (or M) curves for the Bi-Sr-Ca-Cu-O system. They found that at a constant driving force and temperature, U is considerably higher for 2245 samples than for 2223 samples. This enhancement can be attributed to the flux pinning from finely dispersed calcium- and copper-rich precipitates.<
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