Dynamic spin polarization in organic semiconductors with intermolecular exchange interaction

TL;DR

This paper demonstrates that exchange interactions in organic semiconductors induce room-temperature dynamic spin polarization, affecting magnetoresistance behavior and dependent on the relative energies of exchange, Zeeman, and hyperfine interactions.

Contribution

It reveals the role of exchange interaction in generating spin polarization and modifying OMAR lineshape in organic semiconductors, a novel insight into spin dynamics.

Findings

Exchange interaction causes dynamic spin polarization at room temperature.

Spin polarization depends on exchange energy being comparable to Zeeman and hyperfine energies.

Exchange modifies the lineshape of organic magnetoresistance (OMAR).

Abstract

It is shown that in organic semiconductors where organic magnetoresistance (OMAR) is observed, the exchange interaction between electrons and holes localized at different molecules leads to dynamic spin polarization in the direction of the applied magnetic field. The polarization appears even at room temperature due to the non-equilibrium conditions. The strong spin polarization requires exchange energy to be comparable with Zeeman energy in the external field and be larger or comparable with the energy of hyperfine interaction of electron and nuclear spins. The exchange interaction also modifies the lineshape of OMAR.