Manganese based multiferroics, such as BiMnO3, YMnO3, HoMnO3, TbMnO3, etc, have received an attention due to fundamental physics underlying and their potential for various spintronic application such in READ and WRITE heads, field and temperature sensors, spin valves, spin filters, tunnel junctions, p-n junction diodes, non-volatile random access memory devices,etc.In order to explore various applications of doped and un-doped manganite multiferroic, at nanoscale regime, sintering temperature during the synthesis process, is the key factor. This book covers the effect of crystallite size on the dielectric behavior of Ca-doped YMnO multiferroic and study the sintering temperature induced effect of oxygen vacancies on the dielectric permittivity and relaxation mechanism.