A challenge in molecular spintronics is to control the magnetic coupling between magnetic molecules and magnetic electrodes to build efficient devices. Here we show that the nature of the magnetic ion of anchored metal complexes highly impacts the exchange coupling of the molecules with magnetic substrates. Surface anchoring alters the magnetic anisotropy of the cobalt(II)-containing complex (Co(Pyipa)2), and results in blocking of its magnetization due to the presence of a magnetic hysteresis loop. In contrast, no hysteresis loop is observed in the isostructural nickel(II)-containing complex (Ni(Pyipa)2). Through XMCD experiments and theoretical calculations we find that Co(Pyipa)2 is strongly ferromagnetically coupled to the surface, while Ni(Pyipa)2 is either not coupled or weakly antiferromagnetically coupled to the substrate. These results highlight the importance of the synergistic effect that the electronic structure of a metal ion and the organic ligands has on the exchange interaction and anisotropy occurring at the molecule–electrode interface.

Spindependent hybridization at the ferromagnet/molecule interface has recently unveiled a promising new potential for spintronics. By projecting the spintronic properties (i.e. induced spin polarization) from a given ferromagnet electrode to the highly versatile and tailorable molecular layer, spindependent hybridization has opened up new opportunities to tailor spintronic device properties at the molecular scale. Here we focus on the potential and impact of this hybridization on spintronic devices. Depending on the coupling strength at the ferromagnet/molecule interface, the induced spin polarization can be enhanced or even inversed. In the first part of the paper, we introduce the concept of spindependent hybridization and, in particular, we show that it allows the magnetoresistive response of spintronic devices to be tuned. In the second part, we review the experimental evidence emphasizing spindependent hybridization in molecular layers and single molecules. In the last part, we highlight how this spindependent hybridization can play a key role in tunnelling magnetoresistance and tunnelling anisotropic magnetoresistance.

Molecular and organic spintronics is an emerging research field which combines the versatility of chemistry with the non-volatility of spintronics. Organic materials have already proved their potential as tunnel barriers (TBs) or spacers in spintronics devices showing sizable spin valve like magnetoresistance effects. In the last years, a large effort has been focused on the optimization of these organic spintronics devices. Insertion of a thin inorganic tunnel barrier (Al2O3 or MgO) at the bottom ferromagnetic metal (FM)/organic interface seems to improve the spin transport efficiency. However, during the top FM electrode deposition, metal atoms are prone to diffuse through the organic layer and potentially short-circuit it. This may lead to the formation of a working but undesired FM/TB/FM magnetic tunnel junction where the organic plays no role. Indeed, establishing a protocol to demonstrate the effective spin dependent transport through the organic layer remains a key issue. Here, we focus on Co/Al2O3/Alq3/Co junctions and show that combining magnetoresistance and inelastic electron tunnelling spectroscopy measurements one can sort out working “organic” and short-circuited junctions fabricated on the same wafer.