Gadolinium-doped EuS-ZnS core-shell nanocrystals are prepared by solution-phase synthesis. Nanocrystals (NCs) of europium sulfide (Eg=1.64 eV) are of interest for data storage and magnetic refrigeration because they are ferromagnetic (bulk TC= 16.9 K) and exhibit giant magnetocaloric effects. Doping EuS with gadolinium exploits the unique coupling between magnetic, optical, and electronic properties caused by delocalization of the f electrons into the d orbitals. This allows coupling between the magnetic f electrons and the charge carriers, a prominent feature in Dilute Magnetic Semiconductors. This phenomenon has been shown to strengthen coupling between f electrons of Eu2+ ions throughout the bulk material, evidenced by an increased TC. However, doping NCs is more complicated because imperfections in the lattice at the surface can have a significant effect on electrical and optical properties due to the high surface to volume ratio. The effects of surface trap states and surface passivation on the electronic properties of EuS NCs are largely unexplored. Previous photoluminescence studies on a wide range of semiconductor NCs have demonstrated that zinc sulfide shells can augment optical properties by inhibiting carrier quenching at surface trap states. Here, we explore the effects of ZnS shells on the magnetic and optical properties of Gd-doped EuS-ZnS NCs and compare our results to previously reported EuS NCs. Products are characterized for crystallinity, composition, size, morphology, magnetic, and optical properties.

Eu(1-x)Gd(x)S-ZnS core-shell nanocrystals: Synthesis, magnetic, and optical properties

254th National Meeting (2017)

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