The present book consists of six chapters. CHAPTER-I is an introductory chapter. A brief description is given about various types of ferrite materials which include spinels, garnets and hexagonal ferrites. Since the present study deals with the properties of Co-Zr substituted hexagonal M-type barium ferrites,CHAPTER-II deals with the details of preparation of the Ba-Co-Zr ferrites used in the present investigation by the conventional double sintering ceramic method. The XRD was carried out with a Philips X'Pert,In CHAPTER-III, the electrical conductivity of Ba-Co-Zr-ferrites has been investigated by two probe method as a function of composition and temperature using a HR Keithley Electrometer Model 6517A.In CHAPTER- IV, thermoelectric power of Ba-CO-Zr ferrites has been studied as a function of composition and temperature by differential method.Frequency dependence of the real and imaginary parts of permittivity for Co-Zr doped BaFe12O19 ferrites is studied in the range of 1MHZ to 1.8GHZ at room temperature by using Agilent 4291 B impedance analyzer. These results are presented in CHAPTER-V.The magnetic properties of Ba-Co-Zr ferrites are studied by using VSM in CHAPTER VI.