An Organic Spin Valve Embedding a Self-Assembled Monolayer of Organic Radicals

A novel functionalization of a ferromagnetic electrode employed in spintronic devices is reported. Self-assembling monolayer technique has been used to chemisorb a paramagnetic phosphonate functionalized nitronyl-nitroxide radical (NitPO) on the ferromagnetic La0.7Sr0.3MnO3 (LSMO) manganite surface. This interfacial layer causes clearly detectable modifications of the behavior in prototypical LSMO/NitPO/Gaq(3)/AlOx/Co vertical spintronic devices at temperatures below the ferromagnetic alignment (estimated by density functional theory) of the magnetic moments of NitPO and LSMO. This behavior can be justified by a significant spin filtering effect at the engineered interface, with a carrier selection (spin-up) opposite to that of the LSMO/Gaq(3) interface (spin-down). It is proposed that the engineering of spin injecting interfaces with molecules having magnetic moment enables additional mechanisms to control and manipulate the spin polarization of currents in spintronic devices.