Magnetic Properties of Doped II–VI Semiconductor Nanocrystals

We investigate the magnetic properties of two typical II–VI semiconducting nanocrystals, namely, ZnS and ZnO, doped with various concentrations of a transition metal ion, Mn. A wide range of dopant concentrations was explored without changing the size of the nanocrystal, thereby allowing us to study the concentration dependence of various properties independent of any size variation of the host. However, only small doping concentrations could be realized in each case. All the studies were thus carried out with ZnS and ZnO nanocrystals with their respective average sizes fixed at about 1.6 and 4.7 nm. We show that the magnetic properties of such doped systems, remaining paramagnetic down to the lowest temperature (<3 K), can provide important and accurate information concerning the dopant level in such samples.