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 cryst alline Ba0.63K0.37BiO3 superconducting thick film reveal a pronounced depen dence of the "second magnetization peak" (SMP) on sample geometry, i.e. a m aximum in the width of M(H) occurring at the field H-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 t he SMP. Our results can be understood considering the thermomagnetic instab ility effect and/or non-uniform current distribution at H < H-SMP in large enough samples. (C) Elsevier Science Ltd. All rights reserved.