Tuning of reduced remanent and (BH)max by exchange spring phenomenon in ferrimagnetic composite

The (x)% BaFe12O19 (BHF) + (100-x)% CoFe2O4 (CFO) (x = 0 to 100) magnetic composites are prepared to explore its magnetic properties. The XRD patterns reveal the presence of both BaFe12O19 and CoFe2O4 crystal symmetries in the composite. The FESEM and TEM micrographs reveal the uniform distribution of nanoparticles. The theoretical saturation magnetization is calculated by Vegard's law, which is nearly equal to the experimental observation. The maximum reduced remanent (M-r/M-s) and magnetic energy product (BH)(max) are found to be 0.43 and 0.456 MGOe, respectively, for x = 50 i.e. (50)% BHF + (50)% CFO. It is explained by assuming magnetic interaction at the interfaces of soft and hard magnetic phases. The coercive field, remannet magnetization, reduced remanent, saturation magnetization, and (BH)(max) increase with a decrease in measuring temperatures. The enhancement of magnetic parameters at a low temperature is observed due to the decrement of the thermal energy of magnetic moments at the surface. The saturation magnetization increases with an increase in annealing temperature, which could be due to the minimization of spin disorders at the surface of nano-particles. The enhanced reduced remanent (M-r/M-s) and (BH)(max) are found for the (50)%BHF + (50)%CFO composite annealed at a higher temperature. The evidence of magnetic interaction between two magnetic phases in the composite has been realized by employing the Henkel plots and dM/dH versus H curve techniques.

Automated summary

In this study, magnetic composites with varying proportions of BaFe12O19 and CoFe2O4 were prepared and their magnetic properties were investigated. The results show that the nanoparticles are uniformly distributed in the composite, and the saturation magnetization and magnetic energy product of the material can be controlled by changing the proportion. The magnetic parameters also change with annealing temperature and measuring temperature.