Magnetic properties of ZnO-based diluted magnetic semiconductors

We report a study of the magnetic properties of transition-metal doped Zn1-xTMxO (TM=Mn, Co, Fe). Polycrystalline powder samples were synthesized by both solid-state and liquid-phase reactions. From the Curie-Weiss behavior of susceptibility at high temperatures, it was found that the TM-TM interaction is dominated by antiferromagnetic coupling with effective nearest-neighbor exchange constants J= -90 to -30 K. The magnetization data measured at low temperature as a function field H are fit to a parameterized Brillouin function to obtain the effective concentration x(eff) of magnetically active TM2+ ions. As x increases, the fraction of magnetically active ions, x(eff)/x, decreases. This is ascribed to an increase in average AF interaction between doped magnetic spins as the average distance between them decreases with an increase in x. (C) 2003 American Institute of Physics.