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Tunable magnetic exchange interactions in manganese-doped inverted core–shell ZnSe–CdSe nanocrystals

Nature Materials volume 8, pages 35–40 (2009)Cite this article

Abstract

Magnetic doping of semiconductor nanostructures is actively pursued for applications in magnetic memory and spin-based electronics1,2. Central to these efforts is a drive to control the interaction strength between carriers (electrons and holes) and the embedded magnetic atoms3,4,5. In this respect, colloidal nanocrystal heterostructures provide great flexibility through growth-controlled ‘engineering’ of electron and hole wavefunctions in individual nanocrystals6,7. Here, we demonstrate a widely tunable magnetic sp–d exchange interaction between electron–hole excitations (excitons) and paramagnetic manganese ions using ‘inverted’ core–shell nanocrystals composed of Mn2+-doped ZnSe cores overcoated with undoped shells of narrower-gap CdSe. Magnetic circular dichroism studies reveal giant Zeeman spin splittings of the band-edge exciton that, surprisingly, are tunable in both magnitude and sign. Effective exciton g-factors are controllably tuned from −200 to +30 solely by increasing the CdSe shell thickness, demonstrating that strong quantum confinement and wavefunction engineering in heterostructured nanocrystal materials can be used to manipulate carrier–Mn2+ wavefunction overlap and the sp–d exchange parameters themselves.

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Figure 1: An ‘inverted core–shell’ approach to tuning sp–d spin-exchange interactions in heterostructured colloidal nanocrystals.
Figure 2: Magnetic-field- and temperature-dependent Zeeman spin splitting, ΔEZ, and MCD spectra from both magnetic and non-magnetic core–shell nanocrystals.
Figure 3: Field-dependent Zeeman splitting of the 1S absorption peak, ΔEZ, and corresponding effective exciton g-factors at T=1.6 K.
Figure 4: Energy level diagrams illustrating the Zeeman splitting at the nanocrystal absorption edge, in both an exciton and an electron–hole picture.

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Acknowledgements

We thank B. Prall for technical assistance. This work was supported by Los Alamos LDRD Funds and the Chemical Sciences, Biosciences, and Geosciences Division of the Office of Basic Energy Sciences, Office of Science, US Department of Energy (DOE). D.A.B. and V.I.K. are partially supported by the DOE Center for Integrated Nanotechnologies jointly operated by Los Alamos and Sandia National Laboratories. A.L.E. acknowledges financial support from ONR.

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Authors and Affiliations

  1. Chemistry Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA

    David A. Bussian, Ming Yin & Victor I. Klimov

  2. Center for Integrated Nanotechnologies, Los Alamos, New Mexico 87545, USA

    David A. Bussian & Victor I. Klimov

  3. National High Magnetic Field Laboratory, Los Alamos, New Mexico 87545, USA

    Scott A. Crooker

  4. Department of Chemistry, University of California, Davis, California 95616, USA

    Marcin Brynda

  5. Naval Research Laboratory, Washington, District of Columbia 20375, USA

    Alexander L. Efros

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  1. David A. Bussian
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Correspondence to Scott A. Crooker or Victor I. Klimov.

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Bussian, D., Crooker, S., Yin, M. et al. Tunable magnetic exchange interactions in manganese-doped inverted core–shell ZnSe–CdSe nanocrystals. Nature Mater 8, 35–40 (2009). https://doi.org/10.1038/nmat2342

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