Effects of Pr-contents on the structural, magnetic and high frequency parameters of M-type hexagonal ferrites synthesized by sol–gel method

A series of M-type hexagonal ferrite having chemical formula Ba0.75Ca0.25PrxFe12−2xO19 (x = 0.00, 0.50, 1.00, 1.50, 2.00) were prepared by using sol–gel auto combustion technique. These samples were firstly calcined at 900 °C for 3 h and finally sintered at 1150 °C for 5 h. The effects of Pr-contents on the structural, magnetic, and electrical properties of M-type hexaferrite have been studied. The structure and morphology of the samples were studied by X-ray diffraction (XRD) and scanning electron microscopy respectively. Vibrating sample magnetometer was also used in order to study the magnetic properties of these ferrites. XRD patterns show that the samples have single phase M type Ba-hexagonal structure for x = 0.0, 0.5, 1.0 whereas at higher Pr concentrations (x = 1.5, 2.0) some peaks of Fe2O3 appear as second phase. The large value of coercivity (>1 kOe) for all the samples shows that these ferrites are permanent magnets and exhibit the hard magnetic behavior. The variation of AC conductivity and resistivity as a function of frequency could be explained on the basis of Koop’s Phenomenological theory and Maxwell–Wagner model. The observed variation in dielectric constant can be described on the basis of space charge polarization and hopping conduction between Fe+3 and Fe+2. The dispersion observed in the dielectric loss was due to Maxwell–Wagner interfacial type polarization and Koop’s phenomenological theory.