Doctoral Thesis / Dissertation from the year 2010 in the subject Physics - Nuclear Physics, Dr. Babasaheb Ambedkar Marathwada University (-), course: PH.D., language: English, abstract: Wide scope is available to study these aspects of ferrite which at present to our knowledge was not probe by researchers. In relevance to the ever expanding possibilities, and potential that is available with the ferrite materials, the scope of presently undertaken work is designed carefully by selecting suitable ferrite and dopants. A sincere attempt was made to extract fruitful, exhaustive and, systematic information regarding structural, cation distribution, electrical, dielectric and magnetic aspects of the ferrite systems under investigations. In the present study, the properties of nickel ferrites substituted by diamagnetic Zn2+, non-magnetic trivalent In3+ ions and tetravalent Ce4+ ions are studied for various compositions. The properties are investigated with a view to understand the effect of divalent, trivalent and tetravalent substitution in nickel ferrite. The thesis consists of five chapters. Chapter 1 related to Scope, problem statement, theory of magnetism, ferrites, background, motivation and aim of the present work, properties of the samples under investigations, objective and outline of thesis. Chapter 2, 3 and 4 related to results and discussion of structural, electrical and magnetic properties of Ni1-xZnxFe2O4, NiInxFe2-xO4 and Ni1-2xCexFe2O4 ferrite system respectively. Chapter 5 gives the summary, discussion and conclusion on Zn, In and Ce substituted nickel ferrite. On summarizing the results obtained on Ni-Zn, Ni-In and Ni-Ce spinel ferrites it can be concluded that; . The structural properties are found to be varying in all the three systems. The lattice parameter of Ni ferrite systems increases with increasing valancy of dopants (Zn2+, In3+ and Ce4+). . The other prominent parameter of our structural study i.e. porosity reflects that with tetravalent substitution minimum porosity can be achieved. . The particle size does not show any significant difference in their values when substituted with Zn2+, In3+ and Ce4+. . The band frequency in IR spectra slightly changes with the substitution of Zn2+, In3+ and Ce4+. . The magnetic properties are very much affected as can be seen from the values of saturation magnetization of Zn2+, In3+ and Ce4+ substituted nickel ferrite.