Effect of the sample geometry on the second magnetization peak in single crystalline Ba sub(0.63)K sub(0.37)BiO sub(3) thick film

Magnetization hysteresis loop M(H) measurements performed on a single crystalline Ba sub(0.63)K sub(0.37)BiO sub(3) superconducting thick film reveal a pronounced dependence of the `second magnetization peak' (SMP) on sample geometry, i.e. a maximum in the width of M(H) occurring at the field H sub(SMP)(T). In particular, it is found that the SMP vanishes with decreasing film dimension. We argue that the observed sample geometry dependence of the SMP cannot be accounted for by models which assume a vortex pinning enhancement as the origin of the SMP. Our results can be understood considering the thermomagnetic instability effect and/or non-uniform current distribution at H < H sub(SMP) in large enough samples.