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 Ba0.5Sr0.5Fe12−2xCox(MgZn)x/2O19 (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 Ba0.5Sr0.5Fe12O19-phase with space group of P63/mmc. However, in the case of SPS sample with x=0.4, a secondary peak of α-Fe2O3 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, MS (58emu/g) and coercivity, HC (3.5kOe) were obtained for the CS samples with x=0.4; while their SPS counterparts revealed increased MS (65emu/g) and HC (3.9kOe) 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.