Ga 1-x Mn x As nanowires were synthesized with finely controlled Mn contents (x ) 0, 0.01, 0.02, 0.03, and 0.05) by the vapor transport method. They consisted of single-crystalline GaAs nanocrystals (avg. diameter ) 60 nm) grown along the [111] direction. The Mn doping decreases the lattice constant, most significantly at x ≈ 0.03. X-ray photoelectron spectroscopy revealed that as the Mn content increases, the binding energy of Ga 2p shifts to a higher energy, which can be correlated with the hybridization between the Mn 2+ ions and the holes. X-ray absorption spectroscopy and X-ray magnetic circular dichroism confirmed that the Mn 2+ ions substitute into the tetrahedrally coordinated Ga sites and that the magnetic moment is maximized at x ) 0.03, where the lattice constant is minimized and the binding energy of Ga 2p is maximized. The magnetization measurement revealed that all of these nanowires exhibited roomtemperature ferromagnetic behavior, which is also observed most significantly for x ≈ 0.03.

Ferromagnetic Mn-doped In(0.05)Ga(0.95)As and GaAs(0.95)Sb(0.05) nanowires were synthesized by chemical vapor transport and their Mn concentration was about 2%. The Mn doped homogeneously into both the single-crystalline zinc blende InGaAs and GaAsSb without the formation of metal clusters. X-ray magnetic circular dichroism and magnetic moment measurements revealed their distinctive room-temperature ferromagnetic behaviors. While the incorporation of In enhances the ferromagnetism, that of Sb reduces it, which can be ascribed to the increase or decrease of the dopant-acceptor hybridization. These GaAs-based NWs exhibit an efficient terahertz emission at room temperature, due to a strong local field enhancement by coherent surface plasmons. The Mn doping significantly enhances the intensity and bandwidth of the terahertz emission, with an excellent correlation with their magnetization.