Defect-induced magnetism in undoped wide band gap oxides: Zinc vacancies in ZnO as an example

Abstract

To shed light on the mechanism responsible for the weak ferromagnetism in undoped wide band gap oxides, we carry out a comparative study on ZnO thin films prepared using both sol-gel and molecular beam epitaxy (MBE) methods. Compared with the MBE samples, the sol-gel derived samples show much stronger room temperature ferromagnetism with a magnetic signal persisting up to ∼740 K, and this ferromagnetic order coexists with a high density of defects in the form of zinc vacancies. The donor-acceptor pairs associated with the zinc vacancies also cause a characteristic orange-red photoluminescence in the sol-gel films. Furthermore, the strong correlation between the ferromagnetism and the zinc vacancies is confirmed by our first-principles density functional theory calculations, and electronic band alteration as a result of defect engineering is proposed to play the critical role in stabilizing the long-range ferromagnetism

Emergent ferromagnetism in ZnO/Al2O3 core-shell nanowires: Towards oxide spinterfaces

“…Ferromagnetism has been observed previously in undoped thin films and nanoparticles of TiO 2 , HfO 2 , In 2 O 3 , CaO, and CeO 2 . 43,44 This phenomenon is generally recognized as the d 0 magnetism, [45][46][47][48][49] and its origin is usually linked to structural defects. 43,44,50 But the d 0 magnetism is usually very weak, comparable to the magnetic signal observed in our as-grown ZnO NW sample (UZO).…”

An alternative approach to investigate the origin of p-type conductivity in arsenic doped ZnO

“…Despite the above theoretical predictions, no satisfactory experimental observations are available in the literature to justify the source of p-type conductivity. Coincidentally, as a matter of concern, defects in ZnO could also induce ferromagnetism [20]. However, in those theoretical studies, authors did not investigate whether magnetism has been induced on arsenic doping.…”

Effect of Ag on structural, optical and luminescence properties of ZnS nanoparticles synthesized by microwave-assisted chemical route

“…Transition metal ion-doped ZnS nanoparticles are studied extensively to explore their structural, optical, luminescence and magnetic properties. The literature shows that many authors have reported the transition metal ion (Mn, Co, Ni, and Fe)-doped ZnS nanoparticles with different techniques [5][6][7][8][9][10][11][12]. ZnS exists in cubic and hexagonal structure with wide bandgap of 3.54 and 3.91 eV, respectively, and therefore becomes the potential candidate among II-VI group to tailor its properties [13][14][15].…”