ENHANCED FERROMAGNETIC PROPERTIES OF SPINEL Ni0.25Mn0.25Cu0.15Zn0.35Fe2O4 CERAMICS SYNTHESIZED VIA THE SOLID-STATE COMBUSTION

Ni0.25Mn0.25Cu0.15Zn0.35Fe2O4 (NMCZF) soft ferrite ceramics were successfully synthesized using the solid-state combustion. The samples were calcined at temperatures ranging from 900 to 1,000°C for 2 h and sintered between 1,100 and 1,250°C for 5 h. A pure cubic spinel-based ferrite structure was observed in the NMCZF powder calcined at 1,000°C for 2 h. The phase structure, microstructure, dielectric, and ferromagnetic properties of the NMCZF ceramics were investigated. Field emission scanning electron microscopy (FESEM) showed that the average grain size increased with increasing sintering temperature. The measured density of the NMCZF ceramics increased from 5.01 g/cm3 to 5.14 g/cm3 as the sintering temperature increased from 1,100oC to 1,150oC but slightly decreased to 5.09 g/cm3 and 5.07 g/cm3 at temperatures of 1,200oC and 1,250oC, respectively. The frequency-dependent dielectric properties were measured across the 100 Hz to 1 MH frequency range at room temperature. Results showed that the dielectric constant and dielectric loss were frequency-dependent for all samples. The dielectric constant (e) at 100 Hz increased from 354 to 860 with higher sintering temperatures. Under a magnetic field of 15 kOe, the NMCZF ceramics exhibited a typical ferromagnetic response with saturated magnetization. The maximum saturation magnetization (Ms) of 95.2 emu/g and the minimum coercive field (Hc) of 5.3 Oe was observed at a sintering temperature of 1,150°C.