Magnetic instabilities in hard superconductors

This review treats magnetic instabilities in hard and combined Type II superconductors. We give and discuss in detail the criteria for stability of the critical state with respect to magnetic-flux jumps. We study the effect of magnetic and thermal diffusion, as well as that of the structure of a combined superconductor, on the magnetic-field value for a flux jump. The theoretical results are compared with the existing experimental data.