CoxCu1–xCr2S4Nanocrystals: Synthesis,Magnetism, and Band Structure Calculations.

Spin-based transport in semiconductorsystems has been proposedas the foundation of a new class of spintronic devices. For the practicalrealization of such devices, it is important to identify new magneticsystems operating at room temperature that can be readily integratedwith standard semiconductors. A promising class of materials for thispurpose is magnetic chromium-based chalcogenides that have the spinelstructure. Nanocrystals of CoxCu1–xCr2S4have been synthesizedover the entire composition range by a facile solution-based method.While CuCr2S4is a ferromagnetic metal, CoCr2S4is known to be a ferrimagnetic semiconductor.Systematic changes in the lattice parameter, size, and magnetic propertiesof the nanocrystals are observed with composition. The nanocrystalsare magnetic over the entire range, with a decrease in the magnetictransition temperature with increasing Co content. Band structurecalculations have been carried out to determine the electronic andmagnetic structure as a function of composition. The results suggestthat ferrimagnetic alignment of the Co and Cr moments results in adecrease in magnetization with increasing Co concentration. [ABSTRACT FROM AUTHOR]