First order phase transitions of magnetic materials : broad and interrupted transitions This book introduces new concepts in the phenomenon of 1st order phase transitions. It discusses the concept of kinetic arrest at a certain temperature with this temperature being dependent on the second control variable (magnetic field or pressure). It discusses interesting manifestations of this phenomenon when the 1st order transition is broadened i.e. occurs over a finite range of temperatures. Many examples of this phenomenon observed recently in many materials will also be discussed Phase transitions and rigorous definitions Modern classification of phase transitions Defining characteristics of first order transitions Metastable and arrested unstable states across first order transitions Disorder broadened transitions