Ferromagnetism and Giant Paramagnetism of Copper Nanoparticles in Carbon Matrix

Systematic X-ray diffraction, transmission electron microscopy (TEM), Raman and magnetic measurements were performed to study the structural and magnetic properties of copper nanoparticles (NPs) in carbon matrix. The weight concentration of Cu in carbon matrix is 8 wt%. The carbon-coated core-shell structures with bimodal size distribution with 4 and 300 nm average sizes of NPs are confirmed by scanning electron microscopy and TEM. Our results on magnetization carried out by vibrational magnetometer for copper NPs provide a strong evidence for coexistence of ferromagnetism and giant paramagnetism in wide range of temperature and magnetic field. The magnetic susceptibility at T = 10 K shows high value of giant paramagnetism with χ = 5×10
^-5
emu/gCuOe while ferromagnetic behavior with hysteresis is preserved up to the room temperature.