Fashioning spintronics on self-assembled monolayers
Electrons travelling over long distances without losing their spin polarisation as well as control over spin polarisation are important benchmarks for innovative spintronic devices. Compared to their inorganic counterparts, organic materials have low spin-orbit coupling that enables them to retain their spin for long, which is highly desirable for information storage applications. Research has shown that spin-dependent hybridisations at interfaces between ferromagnetic electrodes and molecules enable the control of both magnetism and spin polarisation. The main focus of the EU-funded project SAMSFERE (Self-assembled monolayers over ferromagnetic electrodes for organic spintronics) was the study of organic magnetic tunnel junctions based on SAMs. Expanding on the success of their previous work on functionalising LSMO with alkyl phosphonic acid SAMs, researchers studied the influence of SAM grafting on the LSMO electronic properties using different spectroscopic techniques. Results showed that using SAMs as tunnel barriers can dramatically increase tunnel magnetoresistance. Depending on the alkyl chain length, an increase of up to 250 % in tunnel magnetoresistance at low temperatures was reported. Using a recently developed method to recover oxidised ferromagnetic metal surfaces without altering interfacial properties, researchers integrated SAMs into magnetic tunnel junctions using different materials in ferromagnetic electrodes. Results showed that tunnel magnetoresistance was higher in magnetic tunnel junctions based on iron-nickel compared to those based on cobalt. Spin-hybridised states at ferromagnet-molecular interfaces can influence the spin transport properties of spintronics devices and provide radically new functionalities suitable for information technology applications. They could also bring new opportunities in expanding the efficiency limit of organic LEDs.
Keywords
Self-assembled monolayers, organic spintronics, LEDs, ferromagnetic electrodes, SAMSFERE
