Organic magnetoresistance from deep traps

TL;DR

This paper predicts that deep traps in organic semiconductors can cause spin blockades leading to significant room-temperature organic magnetoresistance, with a nonlinear dependence on trap density.

Contribution

It introduces a new mechanism involving singly-occupied traps causing magnetoresistance, quantified through percolation theory, and predicts a substantial effect at room temperature.

Findings

Magnetoresistance can reach approximately 20% due to deep traps.

Singly-occupied traps cause spin blockades affecting transport.

Magnetoresistance depends nonlinearly on trap density.

Abstract

We predict that singly-occupied carrier traps, produced by electrical stress or irradiation within organic semiconductors, can cause spin blockades and the large room-temperature magnetoresistance known as organic magnetoresistance. The blockade occurs because many singly-occupied traps can only become doubly occupied in a spin-singlet configuration. Magnetic-field effects on spin mixing during transport dramatically modify the effects of this blockade and produce magnetoresistance.We calculate the quantitative effects of these traps on organic magnetoresistance from percolation theory and find a dramatic nonlinear dependence of the saturated magnetoresistance on trap density, leading to values $\sim$ 20%, within the theory's range of validity.