We have studied the influence of intrinsic and extrinsic defects in the
magnetic and electrical transport properties of Co-doped ZnO thin films. X ray
absorption measurements show that Co substitute Zn in the ZnO structure and it
is in the 2+ oxidation state. Magnetization (M) measurements show that doped
samples are mainly paramagnetic. From M vs. H loops measured at 5 K we found
that the values of the orbital L and spin S numbers are between 1 and 1.3 for L
and S = 3/2, in agreement with the representative values for isolated Co 2+.
The obtained negative values of the Curie-Weiss temperatures indicate the
existence of antiferromagnetic interactions between transition metal atoms.Comment: To be published in Journal of Materials Scienc
