Observation of magnetism, low resistivity, and magnetoresistance in the near-surface region of Gd implanted ZnO

Ferromagnetic order is observed in Gd ion implanted ZnO crystals after annealing at 650 °C in a vacuum and we find that it is intrinsic and extends to depths of up to 40 nm. The ferromagnetic order is not affected by Gd for concentrations as high as 5% and possibly arises from defect clusters. Magnetoresistance is observed at low temperatures that may be due to spin-tunnelling between the defect clusters or spin-dependent scattering at the defect cluster interfaces. Gd implantation has an advantageous effect where it results in mΩ cm resistivities as well as significant electron doping.