Ferromagnetism and Giant Paramagnetism of Copper Nanoparticles in Cum/C Nanocomposites

Abstract Carbon coated copper nanoparticles, Cu m /C nanocomposites, were synthesized using solid-phase pyrolysis in solid solutions of copper phthalocyanine and metal free copper phthalocyanine, (CuPc) x (H 2 Pc) 1-x where 0 ⩽ x ⩽ 1 . The weight concentration of copper in percentages consistently varies from 0 to 12 wt% and the sizes of copper nanoparticles in samples changes from 2 nm to 500 nm. Samples containing 8 and 12 wt% Cu have a bimodal size distribution. The X-ray diffraction data and HRTEM images show a face-centered cubic structure of Cu nanocrystallites that uniformly distributed in the carbon matrix. The temperature and field dependences of the magnetization in all copper-containing samples exhibit both ferromagnetic and giant-paramagnetic properties in the measured temperature range of 10-300 K. The saturation magnetization of ferromagnetic nanoparticles falls in the range 0.2-1.5 emu/g and weakly depends on the temperature from helium up to the room temperatures. The paramagnetic magnetizations in Cu/C nanocomposites at H = 50 kOe and T = 10 K are practically an order of magnitude higher in all the samples than the ferromagnetic saturation magnetizations. The paramagnetic susceptibilities of the Cu m /C nanocomposites at 10K are of the order of (0.3-1)10 -4 emu/g Cu Oe, which are one and a half to two orders of magnitude higher than the specific paramagnetic susceptibility of the carbon matrix.