Suppression of ferromagnetic order in CuO/Cu2O nanocomposites

11 nm diameter quasi-spherical and single phase CuO/Cu 2 O nanocomposites, with varying CuO:Cu 2 O ratio, were synthesized using solvothermal process. X-ray diffraction patterns refined with the Rietveld method show an evolution of the CuO:Cu 2 O ratio ( %) for the three samples (100:0, 66:34, and 9:91), along with an increased lattice deformation of the CuO unit cell as the amount of Cu 2 O increased: a = 4.653(2) Å, b = 3.411(1) Å, and c = 5.131(1) Å for the single phase CuO nanoparticles, similar to bulk, while a = 4.727(2) Å, b = 3.457(3) Å, and c = 5.247(2) Å for the 9/91 % CuO/Cu 2 O nanocomposites. Magnetic measurements as a function of the temperature ( M vs T ) and as a function of the magnetic field ( M vs H ) nanoparticles indicated the presence of a ferromagnetic phase in the whole range of temperatures for the single phase CuO nanoparticles, as revealed by the persistent hysteresis observed in the M vs H loops. In addition, an enhanced antiferromagnetic contribution, denoted by the increase in the antiferromagnetic susceptibility, χ AF ∼ 4.8 10 −6 emu∙g −1 ∙Oe −1 , is also observed for these single phase CuO nanoparticles, while for bulk CuO, χ AF ∼ 0.6 10 −6 emu∙g −1 ∙Oe −1 . With increasing Cu 2 O content (≥ 34 % Cu 2 O), the ferromagnetic phase is drastically suppressed for all temperatures, whereas the antiferromagnetic contribution at low temperatures (2–5 K) first increases (χ AF ∼ 5.1 10 −6 emu∙g −1 ∙Oe −1 for 34 % Cu 2 O), but then, it gets reduced (χ AF ∼ 1.46 10 −6 emu∙g −1 ∙Oe −1 for 91 % Cu 2 O). These magnetic changes showcase the relevance of the interface effects introduced by the Cu 2 O phase in CuO/Cu 2 O nanocomposites.