We report magnetism in carbon doped ZnO. Our first-principles calculations based on density functional theory predicted that carbon substitution for oxygen in ZnO results in a magnetic moment of 1.78 µ B per carbon. The theoretical prediction was confirmed experimentally. Cdoped ZnO films deposited by pulsed laser deposition with various carbon concentrations showed ferromagnetism with Curie temperatures higher than 400 K, and the measured magnetic moment based on the content of carbide in the films (1.5 − 3.0µ B per carbon) is in agreement with the theoretical prediction. The magnetism is due to bonding coupling between Zn ions and doped C atoms. Results of magneto-resistance and abnormal Hall effect show that the doped films are ntype semiconductors with intrinsic ferromagnetism. The carbon doped ZnO could be a promising room temperature dilute magnetic semiconductor (DMS) and our work demonstrates possiblity of produing DMS with non-metal doping.

We demonstrate, both theoretically and experimentally, that cation vacancy can be the origin of ferromagnetism in intrinsic dilute magnetic semiconductors. The vacancies can be controlled to tune the ferromagnetism. Using Li-doped ZnO as an example, we found that while Li itself is nonmagnetic, it generates holes in ZnO, and its presence reduces the formation energy of Zn vacancy, and thereby stabilizes the zinc vacancy. Room temperature ferromagnetism with p type conduction was observed in pulsed laser deposited ZnO:Li films with certain doping concentration and oxygen partial pressure.

We introduce a simple approach to synthesize high-quality Fe3O4 nanosheets at low temperature. By oxidizing pure Fe substrates in acidic solution on a hot plate maintained at 70 °C, we have grown the nanosheets in large-scale. The samples were characterized by SEM, XRD, TEM, micro-Raman, and VSM. Flowing O2 gas into the solution during oxidation enhances the growth rate of the nanosheets and thereby shortens the growth time from 24 h to 15 min. The magnetic property of the sample was also investigated. This technique can potentially be extended for large-scale synthesis of other metal-oxide nanosheets such as ZnO.

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