Irreversibility in Ba0.625K0.375BiO3

An irreversibility line has been identified in bulk Ba{sub 0.625}K{sub 0.375}BiO{sub 3}, which follows the relation 1{minus}{ital T}/{ital T}{sub {ital c}}{similar to}{ital H}{sup 2/3}. According to the flux-creep model, the magnetic irreversibility is caused by thermally activated flux creep and is closely connected with the field-induced resistive broadening. However, previous resistivity measurements showed that the Ba{sub 0.625}K{sub 0.375}BiO{sub 3} system did not exhibit resistive transition broadening. Thus, an alternative explanation based on the Josephson-coupling model is suggested to interpret the irreversibility observed in Ba{sub 0.625}K{sub 0.375}BiO{sub 3}.