Charge-induced spin polarization in non-magnetic organic molecule Alq$_{3}$

TL;DR

This study demonstrates that electron injection into the non-magnetic organic molecule Alq3 induces spontaneous spin polarization, with magnetic moments increasing linearly with charge, revealing potential for organic spintronic applications.

Contribution

First-principles density-functional theory calculations showing charge-induced spin polarization in Alq3, a non-magnetic organic molecule, highlighting a new mechanism for organic spintronics.

Findings

Electron injection induces spin polarization in Alq3.

Magnetic moment increases linearly with injected charge.

Spin polarization involves nitrogen p_z orbitals and ferromagnetic coupling.

Abstract

Electrical injection in organic semiconductors is a key prerequisite for the realization of organic spintronics. Using density-functional theory calculations we report the effect of electron transfer into the organic molecule Alq$_3$. Our first-principles simulations show that electron injection spontaneously spin-polarizes non-magnetic Alq$_3$ with a magnetic moment linearly increasing with induced charge. An asymmetry of the Al--N bond lengths leads to an asymmetric distribution of injected charge over the molecule. The spin-polarization arises from a filling of dominantly the nitrogen $p_z$ orbitals in the molecule's LUMO together with ferromagnetic coupling of the spins on the quinoline rings.