π-conjugated organic semiconductors have emerged as suitable candidates in spintronic devices mainly thanks to their low spin orbit interaction. One of the most reproduced effects in organic spintronics is the  inverse magnetoresistive  effect in vertical Spin Valves (SV) based on archetypal organic materials Alq₃ and containing half metallic manganite (LSMO) as bottom electrode and Cobalt as the top one. LSMO/Alq₃ and Alq₃/Co interfaces play a key role in the spin injection process; the occurrence of perturbing effects such as intermixing, chemical reactions, formation of dipole layers or molecular disruption  affects both charge and spin injection and thus the device performance.

Reproducible room temperature operation has been attained  on Alq₃ based SV  trough the insertion of thin insulating tunnel barriers (usually 1-2 nm of Al₂O₃ or LiF)  at the  Alq₃/Co interface.

We present a detailed investigation of LSMO and Co ferromagnetic films and their interfaces with Alq3 in presence of buffer insulating layer and we correlate the results with the operation of spin valve device.

In particular, structural information obtained from X-ray reflectivity measurements and High resolution TEM indicates that the presence of the tunnel barrier layer limits the Alq3/Co intermixing. The chemical states at the interfaces has been investigated by High Energy Photoemission Spectroscopy (HAXPES): the insertion of the tunnel barrier reduces the Co-Alq3 interaction, preventing very efficiently changes of the molecular electronic structure within the intermixed region.

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