Composite magnetic powder of Ni3Fe/Fe3O4 type obtained from Fe/NiO/Fe2O3 mixtures by mechanosynthesis and annealing

Fe3O4/Ni3Fe composite powder has been synthetized, starting from Fe, NiO and α-Fe2O3 precursors via mechanosynthesis and annealing, varying the alloy/ferrite ratio. The formation of Fe3O4 is noticed for the composite with low alloy content in the case of the samples milled for 10 h. Formation of Ni3Fe and Fe3O4 does not fully occur after milling for 10 h, in either of the cases and as a consequence, the presence of several intermediate phases can be observed. Annealing at 500 °C for 4 h led to an incomplete reaction between the precursors for the un-milled sample. For the milled and subsequently annealed samples, the complete formation of the composite Fe3O4/Ni3Fe occurs at the milling time of 10 h. The DSC measurements reveal a decrease of the temperature required for the Fe3O4 complete formation upon increasing milling time. The first magnetisation curves reveal a decrease of the magnetisation upon increasing milling time. The value of magnetisation after annealing is higher than the magnetisation value of the milled samples as a result of the complete formation of the ferrite phase and Ni3Fe intermetallic compound.