Copper-doped ZnO (ZnO:Cu) nanoneedles exhibiting room-temperature ferromagnetism were fabricated by an ion beam technique using Cu plate and ZnO film. A saturated magnetization moment of 0.698emu∕cm3 was found in the nanoneedles when a field of 10kOe was applied perpendicular to the substrate, which was 15% larger than the field applied parallel to the substrate. The magnetic ordering of the nanoneedles was enhanced significantly to 0.968emu∕cm3 after annealing of 400°C for 20min. However, the magnetic anisotropy at high field is vanished but an “easy plane” ferromagnetism becomes apparent at low field region. The possible mechanisms of the magnetic ordering and anisotropy in the ZnO:Cu nanoneedles are discussed.

Copper-doped ZnO (ZnO:Cu) films were prepared on silicon substrates by filtered cathodic vacuum arc technique at room temperature using a Zn target containing 5at.% of Cu. Room temperature ferromagnetism was observed in the ZnO:Cu films with saturation magnetization of 0.037μB∕Cu atom. The origin of the ferromagnetism in ZnO:Cu was mainly due to Cu ions substituted into the ZnO lattice. X-ray diffraction, x-ray photoelectron spectroscopy, and transmission electron microscopy revealed that no ferromagnetic-related secondary phase could be detected in ZnO:Cu.

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Copper-doped ZnO (ZnO:Cu) films with Cu content of up to 8.2 at.% were prepared by filtered cathodic vacuum arc technique on plastic substrates. The ZnO:Cu films with 1.3 at.% of Cu exhibited the highest saturated magnetic moment of 0.28 μ B /Cu. The binding species of the Zn 2p 3/2 , and Cu 2p 3/2 peaks are located at around 1022.1 and 933.6 eV respectively, as measured by x-ray photoelectron spectroscopy respectively. This implies that the Cu ions in the films are mainly in divalent states. The magnetic anisotropy of the ZnO:Cu samples under strain were also studied by bending the flexible samples into various directions. The results indicate that strain plays a role in the magnetic anisotropy of the ZnO:Cu films. The electrical transport and annealing measurements of the ZnO:Cu films suggested that Zn interstitial defects have a significant role in the observed ferromagnetism in the ZnO:Cu.