Recent experiments and theoretical studies have proposed that spin-transport in organic semiconductors, in particular in ${\mathrm{Alq}}_3$, may occur in an impurity band. Here we model the electronic and magnetic properties of such an impurity band by treating the effect of disorder in a numerically accurate way. The calculations are carried out by solving the Anderson-Hubbard model within the mean-field approximation and by accounting for magnetic excitations via the Bethe-Salpeter equation. We find that some impurities form clusters where electrons are delocalized, while others develop localized magnetic moments, which are antiferromagnetically correlated. The excitations of these correlated magnetic moments are spin waves, which can enable spin transport.

• Received 15 January 2019
• Revised 26 February 2019

DOI:https://doi.org/10.1103/PhysRevB.99.094413