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High-temperature magnetic ordering in Mn2+- and Co2+-doped ZnO diluted magnetic semiconductors has been predicted theoretically and confirmed experimentally to have different charge-carrier requirements. This paper summarizes some of these experimental and theoretical results and relates the different carrier polarity requirements for 300 K ferromagnetism in Mn2+:ZnO and Co2+:ZnO to differences in the charge-transfer electronic structures of these two materials. [ABSTRACT FROM AUTHOR]

Future spintronics technologies based on diluted magnetic semiconductors (DMSs) will rely heavily on a sound understanding of the microscopic origins of ferromagnetism in such materials. Discoveries of room-temperature ferromagnetism in wide-bandgap DMSs hold great promise, but this ferromagnetism remains poorly understood. Here we demonstrate a close link between the electronic structures and polarity-dependent high-TC ferromagnetism of TM2+:ZnO DMSs, where TM2+ denotes 3d transition metal ions. Trends in ferromagnetism across the 3d series of TM2+:ZnO DMSs predicted from the energies of donor- and acceptor-type excited states reproduce experimental trends well. These results provide a unified basis for understanding both n- and p-type ferromagnetic oxide DMSs. [ABSTRACT FROM AUTHOR]

The article focuses on a study related to activation of high-Tc ferromagnetism in Mn2+-doped ZnO using amines. Researchers reported that high-Tc ferromagnetism in Mn2+:ZnO can be activated reliably by amine binding and calcination, a process interpreted as incorporating nitrogen into the ZnO lattice as a p-type dopant. These results clearly demonstrate that Mn2+:ZnO ferromagnetism is critically sensitive to defects other than the magnetic dopants themselves, offering some insight into the otherwise irreconcilable observations reported previously.