Origin and Enhancement of Hole-Induced Ferromagnetism in First-Row d(0) Semiconductors

The origin of ferromagnetism in d(0) semiconductors is studied using first-principles methods with ZnO as a prototype material. We show that the presence of spontaneous magnetization in nitrides and oxides with sufficient holes is an intrinsic property of these first-row d(0) semiconductors and can be attributed to the localized nature of the 2p states of O and N. We find that acceptor doping, especially doping at the anion site, can enhance the ferromagnetism with much smaller threshold hole concentrations. The quantum confinement effect also reduces the critical hole concentration to induce ferromagnetism in ZnO nanowires. The characteristic nonmonotonic spin couplings in these systems are explained in terms of the band coupling model.

"One-hundred Talents Plan" of the Chinese Academy of Sciences National Basic Research Program of China (973 Program) G2009CB929300 National Natural Science Foundation of China 60521001 60776061U. S. DOE DE-AC36-08GO28308 J. Li gratefully acknowledges financial support from the "One-hundred Talents Plan'' of the Chinese Academy of Sciences. This work was supported by the National Basic Research Program of China (973 Program) Grant No. G2009CB929300 and the National Natural Science Foundation of China under Grants No. 60521001 and No. 60776061. The work at NREL is supported by the U. S. DOE under Contract No. DE-AC36-08GO28308.