Effect of the sample geometry on the second magnetization peak in single crystalline Ba0.63K0.37BiO3 thick film

Magnetization hysteresis loop M(H) measurements performed on a single crystalline Ba0.63K0.37BiO3 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 HSMP(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<HSMP in large enough samples.