One long-standing challenge in spintronics and quantum information processing is the design of new materials with tunable electron spin properties and dynamics. We combine synthetic chemistry with myriad of structural and spectroscopic techniques to study Ti(IV)-based oxide nanocrystals withtunable carrier densities that possess substitutional aliovalent magnetic dopants. In our initial efforts we found that the choice of precursor and its controlled hydrolysis play a vital role in the successful dopant incorporation. This key finding enables the successful doping of colloidal nanocrystals of SrTiO3, BaTiO3, and TiO2 with an array of aliovalent paramagnetic ions at substitutional Ti-sites. We further explored the interplay between dopants and photochemically-added excess electrons that localize at paramagnetic Ti3+ defects. Using variable temperature EPR spectroscopy, we observe drastic acceleration of the spin relaxation time of substitutional Cr3+ dopant ions with the incorporation of fast-relaxing Ti3+ defects through an efficient cross-relaxation process. While investigating the generality of the drastic dopant-defect interaction, we discovered that other dopants such as Fe3+ behave differently in the presence of Ti3+ and instead appear to reduce to the EPR-silent Fe2+ dopants. These results provide a new design strategy and simple post-synthetic method to rapidly manipulate the magnetic properties of localized paramagnetic centers in Ti-based metal oxidesemiconductor nanocrystals.

Reversible control of the aliovalent magnetic dopants in Ti(IV)-based oxide nanocrystals

ACS Spring Meeting 2021

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