  We report on the structural and magnetic characterization of Co0.1Zn0.9O and
Mn0.1Zn0.9O nanopowders obtained by a soft chemistry route. We show that those
samples fired at low temperatures display a ferromagnetic interaction that can
not be attributed to the presence of impurities. A magnetic aging mechanism is
observed, reflecting the key role played by defects in the stabilization of
ferromagnetism in this kind of diluted magnetic semiconductors.
