Thermomagnetic flux-jump instabilities and second magnetization peak in Bi2Sr2CaCu2O8 high-Tc superconducting crystals

Measurements of the magnetization hysteresis loop performed on Bi2Sr2CaCu2O8 high-T-c superconducting single crystals reveal the occurrence of pronounced jumps of the irreversible magnetization at T>40K. In this work we demonstrate their thermomagnetic origin. It is also shown that the low-field hollow in the magnetization hysteresis loops measured at T<40K and leading to the so-called "second magnetization peak," is the manifestation of a thermomagnetic instability effect. it is suggested that the plastic vortes motion triggers the magnetic instabilities.