Reproducible manipulation of spin ordering in ZnCoO nanocrystalsby hydrogen mediation

Through a simple post hydrogen plasma treatment, we show the strong inducement of the room temperature ferromagnetism in Zn 0.9 Co 0.1 O : H nanocrystals fabricated by sol-gel process. X-ray diffraction, high resolution transmission electron microscopy, and neutron high resolution powder diffraction measurements of Zn 0.9 Co 0.1 O nanocrystals before and after hydrogenation process confirmed that there are no structural changes in nanocrystal and any creation of magnetic secondary phase. Nevertheless, the clear ferromagnetic hysteresis loop of the hydrogenated Zn 0.9 Co 0.1 O nanocrystal was observed in superconducting quantum interference device. These results indicate that the ferromagnetism can be derived from a short-range spin ordering by hydrogen mediation in Co doped ZnO.