Ferromagnetism in Mn- and Co-implanted ZnO nanorods

ZnO nanorods with typical lengths and diameters of ∼2 μm and 15-30 nm, respectively, were grown on Ag-coated Si substrate by catalyst-driven Molecular Beam Epitaxy and subsequently implanted with Mn⁺ or Co⁺ ions of dose ranging from 1-5×10¹⁶ cm^-2. The samples were then annealed at 700°C for 5 minutes. The structural properties were unaffected, but they exhibited ferromagnetism that persisted up to temperatures of 225-300 K. Coersive fields were ≤100 Oe even at 10 K. The results are similar to those obtained for implantation of Mn⁺ and Co⁺ ions in bulk, single-crystal ZnO, indicating the promise of nanorods for nanoscale spintronics.