This book presents an in-depth coverage of nonlinear diffusion of electromagnetic fields. The material discussed in the book has direct applications to the analysis of eddy currents in magnetically nonlinear and hysteretic conductors and to the study of magnetization processes in electrically nonlinear superconductors. For this reason, this book provides valuable technical and scientific information to a broad audience of engineers and researchers involved in such diverse areas as design of electric machines, transformers and activators; development of novel technologies for induction heating, electromagnetic shielding and nondestructive testing; analysis of magnetic hysteresis and creep phenomena in superconductors; development of CAD software in electromagnetics; design of magnetic components in power electronics and inductive (writing) heads in magnetic recording.