Ferrite nanoparticles have attracted a lot of promise in different field (Targeted drug delivery, NMR, hyperthermia and etc).In this book, we dealt with synthetic tehnique (Chemical precipitation and Microemulsion) for the synthesis of multicomponent ferrite nanoparticles. We carried out structural and magnetic study of multicomponent ferrite at different temperature. We also studied the effect of Zn doping in different ratio on structural and magnetic properties.We also studied magnetic behavior at different temperature. This book also dealt with synthesis of long nanofibre polyaniline and its composite with multicomponent ferrite. we discussed the effect of polyaniline nanofibre on magnetic properties of ferrite and mechanism of formation of polyaniline nanofibre and polyaniline composite with schematic diagram. So this book will be very helpful for those who are doing work in the field of nanoparticle and its composite