Magnetic doping of anisotropic colloidal nanocrystals

Colloidal nanostructures (NCs) are known for their tunable photo-physical properties by variation of size, shape and composition. Magnetically doped NCs endow them with additional degree of freedom. The confined structures enhance the spin-spin interaction between photo-generated carriers (electron and hole) and spins of the magnetic impurities. Hence, encouraging unique properties, like giant magnetization and large g-factor of the carriers. The degree of magnetization depends on the quantum confinement, the type of impurity, and its position with respect to the host-carrier distribution function.

In the present work, we focus on the generated magnetism in anisotropic colloidal NCs. The investigated platform is Mn doped CdSe/CdS seeded nanorods. The sample was prepared by colloidal wet chemistry where the control of the kinetics shell growth helps to encapsulate the Mn ions in the shell regime. The ESR method confirm the successful doping of the magnetic ions in CdS lattice.

The magneto-optical properties are an indication for these spin-exchange interactions. The first indication was observed in the photoluminescence (PL) spectra recorded at various temperatures and under the influence of various magnetic fields. Those measurements revealed the creation of giant magnetization. The carrier-impurity interaction was further investigated using an optically detected magnetic resonance (ODMR) spectroscopy. The ODMR spectrum presents a change in luminescence intensity due to a magnetic resonance perturbation at the excited state. The experimental results showed a major band, with a split due to Mn interaction with the resident carriers.

The findings of this work showed a control of doping level and positioning as a tool to manipulate spin properties in nano-scaled materials, a topic of main concern in the currently developing spin-based technologies.