Antiferromagnetism in bulk Zn1-xCoxO magnetic semiconductors prepared by the coprecipitation technique -: art. no. 052501

Polycrystalline Zn1-xCoxO diluted magnetic semiconductors have been prepared by coprecipitation technique in the concentration range 0 <= x <= 0.1. Structure, composition analysis, and optical absorption measurements revealed that cobalt is incorporated into the lattice, as Co2+ substituting Zn2+ ions, forming a solid solution with wurtzite structure instead of Co precipitates. Room- and low-temperature magnetization measurements reveal a paramagnetic behavior for the Co-doped ZnO samples with a paramagnetic Co amount smaller than the nominal concentration. chi T versus T evidenced that the remaining Co is antiferromagnetically coupled through oxygen. This is further supported by a simple model that shows that as the Co concentration increases the amount of nearest neighbors Co atoms increases thus giving antiferromagnetic coupling and reducing the paramagnetic contribution. (c) 2005 American Institute of Physics.