Optical properties and ferromagnetism of ternary Cd1−xMnxTe nanocrystals

Cd1−xMnxTe (x = 0, 0.1, 0.2) nanocrystals have been synthesized by mechanical alloying (MA) Cd, Mn, and Se elemental powders. XRD patterns and HRTEM images confirmed the formation of cubic Cd1−xMnxTe nanocrystals. All the diffraction peaks from elemental Cd, Mn, and Te powders disappeared completely in those XRD patterns of as-milled Cd1−xMnxTe nanocrystals for more than 20 h. When the MA process was carried out for 40 h, typical zinc blende structure diffraction mode was exhibited in the XRD pattern. Subsequently, capping the surface of as-milled Cd1−xMnxTe nanocrystals with long chain trioctylphosphine/trioctylphosphine oxide/nitric acid (TOP/TOPO/NA) molecules has achieved colorful dispersion solution, which shows similar optical properties to those CdTe nanocrystals prepared by wet chemical process. The grain size is within the range of 2–8 nm for the capped Cd1−xMnxTe nanocrystals being ball milled for 40 h. The PL excitation peak red shifts to longer wavelength side with increasing Mn concentration. Pure CdTe nanocrystals show ferromagnetism behavior at room temperature, the saturation magnetization value and magnetic hysteresis loop increase with the content of substituting Mn ions within the Cd1−xMnxTe nanocrystals.