Singlet-to-triplet interconversion using hyperfne as well as ferromagnetic fringe felds

M. Wohlgenannt, M. E. Flatté, N. J. Harmon, F. Wang, A. D. Kent, F. Macià

    Research output: Contribution to journalReview article

    Abstract

    Until recently the important role that spin-physics ('spintronics') plays in organic light-emitting devices and photovoltaic cells was not sufficiently recognized. This attitude has begun to change. We review our recent work that shows that spatially rapidly varying local magnetic fields that may be present in the organic layer dramatically affect electronic transport properties and electroluminescence efficiency. Competition between spin-dynamics due to these spatially varying fields and an applied, spatially homogeneous magnetic field leads to large magnetoresistance, even at room temperature where the thermodynamic influences of the resulting nuclear and electronic Zeeman splittings are negligible. Spatially rapidly varying local magnetic fields are naturally present in many organic materials in the form of nuclear hyperfine fields, but we will also review a second method of controlling the electrical conductivity/electroluminescence, using the spatially varying magnetic fringe fields of a magnetically unsaturated ferromagnet. Fringe-field magnetoresistance has a magnitude of several per cent and is hysteretic and anisotropic. This new method of control is sensitive to even remanent magnetic states, leading to different conductivity/electroluminescence values in the absence of an applied field. We briefly review a model based on fringe-field-induced polaron-pair spin-dynamics that successfully describes several key features of the experimental fringe-field magnetoresistance and magnetoelectroluminescence.

    Original languageEnglish (US)
    Article number20140326
    JournalPhilosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences
    Volume373
    Issue number2044
    DOIs
    StatePublished - Jun 28 2015

      Fingerprint

    Keywords

    • Magnetic-feld efect
    • Magnetoresistance
    • Organic spintronics
    • Spin-chemistry

    ASJC Scopus subject areas

    • Mathematics(all)
    • Engineering(all)
    • Physics and Astronomy(all)

    Cite this