Intrinsic magnetism of Zn1-xCoxO single-crystalline nanorods prepared by solvothermal method

We grew Zn1-xCoxO single-crystalline nanorods with x≤0.1 by a solvothermal method and systematically investigated their properties and growth conditions. The nanorods were obtained at low temperature (120–190°) and became thicker and finally transformed into polyhedrons with increasing growth temperature. Impure Co-phase microclusters appeared when the growth temperature exceeds 190°. Co ions appeared in the +2 oxidation state in the nanorods, indicating that they were incorporated into the ZnO lattice. The magnetic properties evolved from a short-range ferromagnetic state at x=0.05 to long-range ferromagnetic order at x=0.10. Our results show that the ferromagnetism observed in Zn1-xCoxO was intrinsic and can be understood within the framework of the percolation of bound magnetic polarons.