Structural and magnetic properties of Ni-Pt nanoalloys supported on silica

Bimetallic Ni-x%Pt/SiO₂ nanoclusters at different initial platinum contents (x = 0, 2, 9, 15, 25, 35, 85 and 95 at %) are synthesized at room temperature by the radiolytic process. According to the Pt amount, the structural studies (XRD, TEM and SAED) reveal the presence after irradiation of NiSi and Ni₃Pt or NiPt₃ nanoalloyed clusters on amorphous silica. The Ni-Pt nanoparticles have a fcc solid solution structure and a narrow cluster size distribution. The radiation-induced nanoparticles exhibit an enhancement of the magnetization at low temperature. Moreover, unlike Ni-Pt bulk alloys, the magnetization increases with the Pt content. In the ultra divided state, platinum seems to play a major role by enhancing the nickel ion reduction and protecting Ni against corrosion during the synthesis.