Synthesis and characterization of Co–Ni and Fe–Ni alloy nanoparticles

• Synthesis of Co–Ni and Fe–Ni alloy nanoparticles by exploiting low temperature sol–gel process.
• The nanoparticles are core–shell type with core ferromagnetic alloys and graphitic carbon shell.
• Electron microscope study explains the higher stability at ambient conditions of the nanoparticles.

The magnetic alloy nanoparticles have been synthesized by sol-gel method with a stable Pm-3m cubic structure. The Co–Ni and Fe–Ni alloy nanoparticles are highly crystalline and exhibit preferential low index <111> faceting as determined from HRTEM investigation. TEM images and EDX elemental mapping also confirm the nano-dimensional structure with core-shell structure, where the alloy forms the core and the shell is formed by amorphous carbon. The magnetization results of the alloy nanoparticles confirm the ferromagnetic nature at room temperature akin to their bulk metals with a significant value of field dependent isothermal magnetization at high temperature (390 K).