Structural and magnetic properties of spark plasma sintered Co-Mg-Zn substituted Ba-Sr hexagonal ferrite magnets

Abstract The effect of conventional and spark plasma sintering processes on the structural and magnetic properties of Ba 0.5 Sr 0.5 Fe 12−2x Co x (MgZn) x /2 O 19 ( x  = 0.2, 0.4 and 0.6) was investigated in this study. XRD patterns of both conventionally sintered (CS) and spark plasma sintered (SPS) samples with x  = 0.2 and 0.4 showed the crystallization of Ba 0.5 Sr 0.5 Fe 12 O 19 -phase with space group of P6 3 /mmc. However, in the case of SPS sample with x = 0.4, a secondary peak of α-Fe 2 O 3 was observed. SEM analysis on the SPS samples revealed dense morphology with low porosity; while the CS samples showed the presence of aggregated particles with spherical shapes. Maximum values of saturation magnetization, M S (58 emu/g) and coercivity, H C (3.5 kOe) were obtained for the CS samples with x  = 0.4; while their SPS counterparts revealed increased M S (65 emu/g) and H C (3.9 kOe) values. The observed magnetization reversal behaviour for both sintering conditions were not smooth in the case of x  = 0.2, which indicated the existence of two-phase behavior. The temperature dependent magnetization studies for x  = 0.2 and 0.4 were performed in order to analyze the variation in Curie temperature against Co-Mg-Zn substitution and the obtained results are discussed on the basis of crystallization of hexaferrite-phase.