Ferrites have been proved as a promising resource for diverse applications in the field of electronics, telecommunication, computer and space technology for last two decades. In addition to this, ferrites continue to be systematically studied further in different forms for their structural and transport properties for identifying their advanced applications. This book deals with the study of Co doped Ni ferrites which shows very interesting and modified variation in the physical properties at a few nanometers size which presents an overview of the synthesis, structural and morphological studies of Co doped Ni ferrites. In addition to this the electrical, dielectric and magnetic properties have been studied in detail to know their conduction mechanism and behaviour of dipole moment. A part of this book introduces new achievements in the field of gas sensing where Ni ferrite acts as an efficient gas sensor at room temperature and this ferrite family is observed to be field sensitive which can be used as field sensors. I am sure that this book would be very useful for the researchers involved in the field of Physics, Chemistry, Metallurgy, Materials Science and Engineering.