Fine powders of micron and sub-micron sized particles of undoped Cu2O, with

three different sizes and morphologies, were synthesized using different chemical

processes. These samples included nanospheres 200nm in diameter, octahedra of

size 1μm and polyhedra of size 800nm. They exhibited a wide spectrum of

magnetic properties. At 5K, the octahedron sample was diamagnetic with the

magnetic susceptibility χOH = −9.5 x 10−6emu/gOe. The nanosphere was

paramagnetic with χNS = 2.2 x 10−5emu/gOe. The other two polyhedron samples

synthesized in different runs by the same process were found to exhibit different

magnetic properties. One of them exhibited weak ferromagnetism with TC~455K

and a saturation magnetization of MS~0.19emu/g at 5K, while the other was

paramagnetic with χ = 1.0 x 10−5emu/gOe. The total magnetic moment estimated

from the detected impurity concentration of Fe, Co and Ni, was too small, to

account for the observed magnetism, by one to two orders of magnitude.

Calculations using density functional theory revealed that cation vacancies in the

Cu2O lattice were one of the possible causes of induced magnetic moments. The

results further predicted that the defect-induced magnetic moments favour a

ferromagnetically coupled ground state if the local concentration of cation

vacancies, nC, exceeded 12.5%. This possibly explained the observed magnetic

properties.

Magnetic Properties of Undoped Cu2O Fine Powders with Magnetic Impurities

and/or Cation Vacancies. C.Chen, L.He, L.Lai, H.Zhang, J.Lu, L.Guo, Y.Li:

Journal of Physics - Condensed Matter, 2009, 21[14], 145601