Syntheses of Ferrite/Metal Composite Powders and Their Magnetic Properties

Abstract

The composite fine powders of nickel zinc ferrite and nickel-iron alloy were synthesized from α-hematite, nickel chloride and zinc by using the thermite method. These starting materials were arranged to mixtures having α-Fe₂O₃:NiCl₂:Zn of 1.0:0.5:X(X=0.5, 1.0, 1.5) and were sufficiently mixed. These samples were heated over the temperature range from 400°C to 600°C for 2 hours under argon gas flow and their crystal phases and magnetic properties of the products were investigated by X-ray diffraction and vibrating sample magnetometer respectively.
The sample with X=0.5 contained only two phase: nickel and spinel phases which were ferromagnetic. Saturation magnetization of the sample was around 70 emu/g. Nickel-iron alloy powders, nickel-zinc ferrite powders and non-magnetic zinc oxides were produced with the increase of zinc amounts and heating temperature. The lattice constant of the ferrite was increased by the formation of nickel zinc ferrite. The value of saturation magnetization of the composite powder prepared with X=1.0 was 89.7 emu/g, which was greatest.
The value of saturation magnetization of the sample with X=1.5, however, decreased because of the increase of non-magnetic zinc oxides.