Doping effects in strontium hexaferrite: Theoretical and experimental analysis

Abstract

Hexagonal ferrites based on SrFe12O19 (SFO) are vital materials in the field of permanent magnets, valued for their cost-effectiveness and reliable magnetic properties, making them a more affordable alternative to rare-earth permanent magnets. This study focuses on understanding the doping effects of commonly used elements in SFO system. DFT calculation results show that doping La or La-Co can enhance the phase stability of SFO, in which Co has a preference for the 4f1 sites of Fe. The total magnetic moment was observed to slightly decrease with La doping, whereas it exhibited an increasing trend with La-Co and La-Ca-Co co-doping and the largest increase of 6.5 % can be obtained in Sr2LaCaFe44Co4O76 (SLCFCO). The increase in the total magnetic moment is mainly attributed to the smaller antiferromagnetic moment of Co than that of Fe on 4f1 sites, as well as the reduction in the antiferromagnetic Fe moments at 4f1 and 4f2 sites. The total density of states indicates a transition from semiconductor behavior to a metallic character both in the La-Co and La-Ca-Co doped versions. The experimental results validate the theoretical predictions, confirming enhancements in magnetic performance. The saturation magnetization increased from 63.86 Am2/kg in SrFe11.7O19 (SFO) to 67.53 Am2/kg in Sr0.4La0.4Ca0.2Fe10.5Co0.5O19 composition. These findings provide a vital understanding of tuning the magnetic and electronic properties in doped SFO, which will enable the development of advanced applications in magnetic materials.