Defect ferromagnetism in ZnO and SnO2 induced by non-magnetic dopants

Sadaf Akbar

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In this thesis we determined that suitable defects (e.g. cationic vacancies) in ZnO and SnO2 systems can enable ferromagnetic behaviour even for small dopant concentrations. We elucidated that the structural, morphological, electronic, magnetic, optical and electrical properties are highly sensitive to the addition of non-magnetic dopants and this sensitivity seems to derive from how the dopants affect the relative concentration of defects. We addressed the crucial question of the specific role played by non-magnetic defects in stabilizing and enhancing ferromagnetism in these oxide systems.
The first part of the PhD project concentrated on the study of carbon-doped ZnO. In the case of C-doped ZnO thin films, we observed room temperature ferromagnetism with n-type conductivity. The ferromagnetism is suggested to originate from Zn vacancies that are stabilized when C is incorporated at zinc sites. We also studied the effects on ferromagnetism of C-doped ZnO powders sintered in either reducing or nitrogen atmosphere.
The second part of the PhD project was focused on studying ferromagnetism in SnO2, doped with non-magnetic dopants, i.e. Zn and Li. For Zn-doped SnO2 system the complex interplay between nanostructures, defect formation and consequent ferromagnetism was demonstrated. The morphology of the nanostructures varies with zinc concentration and the stronger ferromagnetic response comes from nanostructures with nanoneedles on their surfaces. Raman spectra, photoluminescence and band gap variations of Zn-doped SnO2 nanostructures were discussed. We also demonstrated the role of Li as a ferromagnetic defect in SnO2 nanoparticles, which was seen to be less effective as compared to Zn.
Originele taal-2English
KwalificatieDoctor of Philosophy
Toekennende instantie
  • Rijksuniversiteit Groningen
Begeleider(s)/adviseur
  • Rudolf, Petra, Supervisor
  • Hasanain, S.K., Supervisor, Externe Persoon
Datum van toekenning24-feb-2017
Plaats van publicatie[Groningen]
Uitgever
Gedrukte ISBN's978-90-367-9362-9
Elektronische ISBN's978-90-367-9361-2
StatusPublished - 2017

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