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The properties of the core&shell type nanocomposites formed on the steel surface via the rotation-corrosion dispergation route in the presence of precious metal aquahydroxoforms have been studied using physical-chemical multi-methods of the research. Depending on the kind of precious metal only magnetite or magnetite and lepidocrocite are formed in the system. The size of magnetite cores does not exceed 25 nm. The precious metal fraction on the magnetite surface varies from 0.04 to 0.5 wt% and it depends on the initial concentration of the solutions. All samples belong to superparamagnetics and do not show the remanence magnetization and coercitivity. The last parameter equals for Ag-containing system 24, for Au-bearing—48, for Pd-bearing—62, and for Pt-bearing—49 to 60 A m² kg⁻¹.