Abstract
Using density functional theory calculations, we examine the effect of hole doping on the magnetic and electronic properties of CuMIIIAO2, with MIIIA = Al, Ga, and In. CuMIIIAO2 nonmagnetic semiconductors switch to ferromagnetic half-metals upon hole doping. For CuAlO2, the nonmagnetic-to-ferromagnetic transition occurs for hole densities of ∼7 × 1019/cm3. Ferromagnetism arises from an exchange splitting of the electronic states at the valence band edge, and it can be attributed to the high-lying Cu-d states. Hole doping induced by cation vacancies and substitutional divalent dopants is also investigated. Interestingly, both vacancies and nonmagnetic divalent dopants result in the emergence of ferromagnetism.
Highlights
Ferromagnets such as iron, cobalt, and nickel, are typically metals, whereas materials with both ferromagnetic and semiconducting properties are scarce
Contrary to GaAs-based diluted magnetic semiconductors (DMS), room-temperature ferromagnetism has been observed in diluted magnetic oxides such as TiO2, ZnO, and SnO.[6−10] Intriguingly, high-temperature ferromagnetism in the absence of magnetic ions has been reported.[11−21] For instance, Kenmochi et al found that carbon-doped oxides such as MgO, SrO, BaO, and CaO are ferromagnetic without any transition-metal impurities, and based on the mean-field approximation, Curie temperatures higher than room temperature have been predicted.[19−21]
In this paper, using density functional theory (DFT) calculations, we examine the effect of hole doping on the magnetic properties of CuMIIIAO2 with MIIIA = Al, Ga, and In, having CuAlO2 as a prototype material
Summary
Ferromagnets such as iron, cobalt, and nickel, are typically metals, whereas materials with both ferromagnetic and semiconducting properties are scarce. CuAlO2 is an attractive candidate for various applications owing to its p-type conductivity (without intentional doping) and its visible light transparency.[28−30] In general, the design of p-type transparent conductive oxides (TCO) is found to be difficult, and the difficulty arises from the nature of the VB edge, dominated by localized O-2p states.[31,32] Holes are typically trapped at O sites and cannot migrate through the oxide, leading to poor p-type behavior To overcome this limitation, modulation of the VB edge through hybridization of the O-2p orbitals with metal orbitals has been proposed.[31] The discovery of p-type. We find that nonmagnetic divalent dopants result in the emergence of ferromagnetism, and ferromagnetism can be attributed to the high-lying Cu-d states, dominating over the O-p states at the VB edge
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