Magnetic properties of ZnO-based diluted magnetic semiconductors.

We report a study of the magnetic properties of transition-metal doped Zn[SUB1-x]TM[SUBx]O (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 =290 to 230 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[SUBeff] of magnetically active TM[SUP2+] ions. As x increases, the fraction of magnetically TM active ions, x[SUBeff]/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. [ABSTRACT FROM AUTHOR]