Abstract
The selected and controlled preparation of core@shell nanostructures, which unite the multiple functions of ferromagnetic Ni-Zn ferrite core and CdS shell in a single material with tuneable fluorescence and magnetic properties, have been proposed by the seed mediated aqueous growth process. The shell particle thickness and core of nanostructures were precisely tuned. Current work exhibits the comparative study of core@shell multifunctional nanostructures where core being annealed at two different temperatures. The core@shell nanostructure formation was confirmed by complementary structural, elemental, optical, magnetic and IR measurements. Optical and magnetic characterizations were performed to study elaborative effects of different structural combinations of core@shell nanostructures to achieve best configuration with high-luminescence and magnetic outcomes. The interface of magnetic/nonmagnetic NiZnFe2O4/CdS nanostructures was inspected. Unexpectedly, in some of the core@shell nanostructures presence of substantial exchange-bias was observed in spite of the non-magnetic nature of CdS QDs which is clearly an “optically-active” and “magnetically-inactive” material. Presence of “exchange-bias” was confirmed by the change in “magnetic-anisotropy” as well as shift in susceptibility derivative. Finally, successful formulation of stable and efficient core@shell nanostructures achieved, which shows no exchange-bias and shift. Current findings suggest that these magneto-fluorescent nanostructures can be used in spintronics; and drug delivery-diagnosis-imaging applications in nanomedicine field.
Exchange-bias and magnetic anisotropy fields in core–shell ferrite nanoparticles
