Abstract
Zinc Oxide (ZnO) is a potential diluted magnetic semiconductor (DMS) material. Despite of the devoted efforts for more than a decade, the reported outcomes on room temperature ferromagnetism (RT FM) in ZnO based materials have created significant puzzlements. It is thus crucial to comprehend the underlying physics of RT FM and its separation from inconsistent science in this academically and practically curious material. A battery of several characterization techniques has been employed to build a careful and plausible explanation of the magnetic behavior that is unfortunately not simple but needs comprehensive study to unravel. I will highlight the importance of the critical oxygen growth pressures (PO2) to get good epitaxial films with relatively higher Cu2+/Cu1+ ratios. The relative strength of the Cu2+ and Vö controls the Cu2+ – Vö – Cu1+ ferromagnetic channel, which is highly tuned by the PO2. Low temperature (≤ 90K) conductivity data shows a clear transition from band conduction to Mott variable range hopping (VRH) mechanism in the studied systems. A predominant VRH mechanism among randomly distributed Cu2+ – Vö – Cu1+ complexes supports hypothesis of donor-acceptor pair defect model to prevail in these materials. In this talk, physics of RT FM in ZnO:Cu material will be discussed.
Anyone interested is welcome to attend.