Influence of oxygen partial pressure on the ferromagnetic properties of polycrystalline Cr-doped ZnO films

Abstract

Polycrystalline Cr-doped ZnO films are prepared by the co-sputtering method. Diamagnetism is observed in the conductive samples deposited in pure Ar. However, ferromagnetism is found in films with the same Cr dopant prepared under different oxygen partial pressures. The magnetization shows a strong dependence on the Cr concentration and, especially, on oxygen pressure. It is found that native point defects, which can be adjusted by the oxygen partial pressure during deposition, play a crucial role in the observed magnetic behaviors. The obtained ferromagnetism can be described by the dopant-donor/acceptor hybridization model, which associates exchange interaction with shallow-bound carriers. These results may help to understand the wide range of experimentally determined magnetic moments and its changes with different metal types and concentrations prepared by different groups and methods.

Structural, optical and magnetic properties of Ni-doped ZnO micro-rods grown by the spray pyrolysis method

“…The weak UV luminescence peak located at ~ 386 nm, corresponding to a photon energy of ~ 3.21 eV, is related to near band edge emission. Other peaks are found in the visible blue spectral region via the fitting of the entire emission at energies of 3.00 eV, 8 2.84 eV, 2.67 eV and 2.55 eV which may correspond to V Zn , Zn i , V Zn -and V o , respectively, which are in good agreement with other studies in the literature [32,33]. [34].…”

“…by binding the spins of magnetic ions to form bound magnetic polarons, consistent with the hypothesis that such defects may be the origin of the observed room temperature ferromagnetism [32,33,45].…”

Synthesis and characterization of Mn-doped ZnO nanorods grown in an ordered periodic honeycomb pattern using nanosphere lithography

“…On the other hand, undoped ZnO also has a weak broad band betweeen 1.77 and 2.82 eV that is associated with deep level emission (DLE). This band is often associated with intrinsic defects such as Zn i , V Zn -, V o and O i [28,29]. Upon Mn-doping and annealing at 500 and 600…”

Evidence for high-Tcferromagnetism inZnx(ZnO)Zhang1, Cheng2, Li3 et al. 2009Phys. Rev. BSelf Cite690140View full textAdd to dashboardCite

“…[7][8][9][10][11][12][13][14] However, the detailed mechanism is unclear yet. One of the important obstacles is that the chemistry of ZnO defect is sophisticated, including the main defect types of Zn i , Zn vacancy, oxygen interstitial and V O .…”

“…18,19 Despite the pitfalls associated with magnetic precipitates or clusters, careful measurements have yielded significant evidence which indicates that the point defects of ZnO, such as oxygen vacancy ͑V O ͒ or Zn interstitial ͑Zn i ͒, are crucial for ferromagnetism of transition-metal-doped ZnO. [7][8][9][10][11][12][13][14] The recent x-ray magnetic circular dichroism ͑XMCD͒ investigations by Tietze et al 20 even showed that the doped Co atoms were paramagnetic in their ferromagnetic Co-doped ZnO films. Simultaneously, room-temperature ferromagnetism has also been found in undoped HfO 2 , ZnO, and TiO 2 films or partially oxidized Zn nanowires, which was attributed to point defects.…”