Defect-band mediated ferromagnetism in Gd-doped ZnO thin films

• Main Authors: Venkatesh, S., Franklin, J. B., Ryan, M. P., Lee, J.-S., Ohldag, Hendrik, McLachlan, M. A., Alford, N. M., Roqan, I. S.
• Other Authors: Energy Research Institute @ NTU (ERI@N)
• Format: Article
• Language: English
• Published: 2015
• Subjects: DRNTU::Science::Physics
• Online Access: https://hdl.handle.net/10356/106886; http://hdl.handle.net/10220/25222
• Institution: Nanyang Technological University

Gd-doped ZnO thin films prepared by pulsed laser deposition with Gd concentrations varying from 0.02–0.45 atomic percent (at. %) showed deposition oxygen pressure controlled ferromagnetism. Thin films prepared with Gd dopant levels (<Gd 0.112 at. %) at low oxygen deposition pressure (<25 mTorr) were ferromagnetic at room temperature. Negative magnetoresistance, electric transport properties showed that the ferromagnetic exchange is mediated by a spin-split defect band formed due to oxygen deficiency related defect complexes. Mott's theory of variable range of hopping conduction confirms the formation of the impurity/defect band near the Fermi level.