Thermal behavior and magnetic properties of the copper- and cobalt-substituted magnet-ite nanoparticles formed on the steel surface in the open-air system

The optimal physical conditions for obtaining raw materials on the steel surface contacting with cobalt and copper sulfate solutions applying the rotation corrosion dispergation method were deter-mined at T □ 50 °C. The subsequent heating of mixed cobalt and copper containing spinel ferrite and ferric oxyhydroxide powders permits to form monomineral phases of maghemite (T □ 200–220 °C) and hematite (□ 300 °C) doped with respective metals. The difference in magnetic properties of the heated powders lies in the following: whereas copper-containing phases do not display the residual magneti-zation (Mr) and coercitivity (Hc) at T □ 50–740 °C, the saturation magnetization (Ms) of such powders in T range 50–250 °C is ∼ 35 A·m2/kg. But all cobalt-containing samples exhibit Mr ∼ 10 A·m2/kg and He that increases from 0.08 at 50 °C to 0.12 T at 740 °C.