Transition metal dopants essential for producing ferromagnetism in metal oxide nanoparticles

摘要

Recent claims that ferromagnetism can be produced in nanoparticles of metal oxides without the presence of transition metal dopants have been challenged in this work by investigating 62 high-quality well-characterized nanoparticle samples of both undoped and Fe-doped (0-10% Fe) ZnO. The undoped ZnO nanoparticles showed zero or negligible magnetization without any dependence on the nanoparticle size. However, chemically synthesized Zn_(1_x)Fe_xO nanoparticles showed clear ferromagnetism, varying systematically with Fe concentration. Furthermore, the magnetic properties of Zn_(1_x)Fe_xO nanoparticles showed strong dependence on the reaction media used to prepare the samples. The zeta potentials of the Zn_(1_x)Fe_xO nanoparticles prepared using different reaction media were significantly different, indicating strong differences in the surface structure.