The microstructure and magnetic properties of Ni nanoplatelets

Ni nanoplatelets were prepared through the reduction reaction with hydrazine by the sonochemistry method. The obtained Ni nanoplatelets are single-phased Ni and have a face-centred cubic crystal structure. The lattice constant is slightly larger than the corresponding bulk value. The Ni nanoplatelets are plate-like in shape and have an average diameter of 100 nm and an average thickness of 10 nm. An oxidation layer is found on the nanoplatelet surface and this serves to prevent further oxidation. The surface oxidation layer leads to the reduction of the saturation magnetization of the Ni nanoplatelets compared with the bulk value. Magnetic hysteresis loops along different directions deviating from the nanoplatelet plane are obviously different, indicating that the easy-axis is in the in-plane direction and the magnetization reversal is incoherent mode. The micromagnetic simulation results for an array composed of 36 Ni nanoplatelets are in agreement with the measured data.