Spin Properties in Magnetically Doped Semiconductor Nanocrystals

Joanna Dehnel joanna.dehnel@gmail.com ¹ Rotem Carmi ¹ Yahel Barak ¹ Savas Delikanli ^2,3 Alyssa Kostadinov ¹ Itay Meir ¹ Hilmi Volkan Demir ^2,3 Efrat Lifshitz ¹

¹Schulich Faculty of Chemistry, Solid State Institute, Russell Berrie Nanotechnology Institute, Technion, Haifa, Israel
²Electrical and electronics Engineering Department and Physics Department, Bilkent University, Ankara, Turkey
³School of Material Science and Engineering, NTU, Singapore, Singapore

Recently, research interest has shifted toward semiconductors NCs embedded with magnetic ions, joining a group of materials known as diluted magnetic semiconductors (DMS)[1].The magnetic ions provide spin-exchange interaction with carrier spins, resulting in giant enhancement of magneto-optical and magnetic properties of semiconductors. Low-dimensional structures (quantum wells, wires, dots) offer advantage for DMS, as the spatial carrier confinement strongly enhances their exchange interactions with magnetic ions [2].

In the present work, we compare the generated magnetism in colloidal nanocrystals of different morphologies, the quantum dots (QDs), seeded nanorods (NRs) and nanoplatelets (NPLs), all with core/shell configuration based on CdSe/CdS composition with a quasi-type-II core-shell band alignment. Those nanocrystals were embedded with a diluted concentration of Mn⁺² impurities, prepared by colloidal layer-by-layer deposition procedures, controlling the position of the magnetic ions in the shell regime.

The temperature dependence PL studies showed a pronounced Stokes shift of the emission in the doped nanocrystals with respect to that of the undoped structures, stemming from the so-called sp-d interaction. Fitting the experimental data to a Brillouin function revealed a generation of internal magnetization varying from 28 Tesla to 65 Tesla in the various structures. The findings of this work showed a control of doping level and positioning as a tool to manipulate spin properties in nanoscaled materials, a topic of main concern in the currently developing spin-based technologies.

[1] J.K. Furdyna, Journal of Applied Physics, 1988, 64, R29-R64.

[2] W. D. Rice1, W. Liu, V. Pinchetti, D. R. Yakovlev, V. I. Klimov, S. A. Crooker, Nano Lett., 2017, 17 (5), pp 3068–3075.