Reversal of Spin Signals in Anthraquinone-Based Magnetic Tunnel Junctions

Molecular spintronics aims to control spin current transmission in magnetoresistive devices through molecular engineering. By tailoring the chemical structure of organic molecules atom by atom, chemistry offers a powerful route to designing media for spin transport. A key milestone of the field is to tune spin polarization at ferromagnetic metal-molecule interfaces according to their atomic-scale details. In parallel, research focuses on spin transport through functional molecules, such as conformational switches and chiral systems. In this study, we investigate active molecular layers made of anthraquinone (AQ) oligomers. Experimental and theoretical data are presented for Co/graphene/AQ/Co spin-valve junctions fabricated via an electrografting method on graphene-protected electrodes. Observation of bias-dependent spin filtering, including spin polarization reversal, demonstrates a novel LUMO hybridization mechanism that can enable quantum spin-selective effects in future molecular spintronic devices.