Magnetoresistance from quenching of spin quantum correlation in organic   semiconductors
  We present a theory of organic magnetoresistance (OMR) based on the quenching of the quantum correlation between the carrier's spin and its local environment when the incoherent hopping takes place. We prove that this process contributes a spin-dependent prefactor to the attempt-to-escape frequency in the hopping rate, with its value modulated by the magnetic field. The resulting OMR exhibits a positive Lorentzian saturation component and a negative small-field component, which are independent of model parameters. These behaviors, with their isotope effects, are in good agreement with experimental results. 
Wei Si, Yao Yao, Xiaoyuan Hou, Chang-Qin Wu
cond-mat.mtrl-sci cond-mat.mes-hall