Magnetic Semiconductor Quantum Dots

Cdo.5Mno.5S diluted magnetic semiconductor (DMS) quantum dots (QDs) of crystallite size ranging from 24 A to the bulk have been chemically synthesized using an aqueous solution precipitation method and thermal annealing. Subsequent characterization indicates that the "as prepared" material is of the cubic zinc blende structure which evolves with increasing size to the bulk hexagonal wurtzite structure. Magnetic properties of the DMS QDs have been measured with a SQUID magnetometer. A transition from a paramagnetic to a spin-glass (SG) state at a critical temperature T, has been observed. Size dependence measurements on Tf indicate a minimum size for SG formation. Relaxation in isothermal remanent magnetization has also been measured and shows a power law decay.