Tuning of a Vertical Spin Valve with a Monolayer of Single Molecule Magnets

The synthesis and the chemisorption from solution of a terbium bis-phthalocyaninato complex suitable for the functionalization of lanthanum strontium manganite (LSMO) are reported. Two phosphonate groups are introduced in the double decker structure in order to allow the grafting to the ferromagnetic substrate actively used as injection electrode in organic spin valve devices. The covalent bonding of functionalized terbium bis-phthalocyaninato system on LSMO surface preserves its molecular properties at the nanoscale. X-ray photoelectron spectroscopy confirms the integrity of the molecules on the LSMO surface and a small magnetic hysteresis reminiscent of the typical single molecule magnet behavior of this system is detected on surface by X-ray magnetic circular dichroism experiments. The effect of the hybrid magnetic electrode on spin polarized injection is investigated in vertical organic spin valve devices and compared to the behavior of similar spin valves embedding a single diamagnetic layer of alkyl phosphonate molecules analogously chemisorbed on LSMO. Magnetoresistance experiments have evidenced significant alterations of the magneto-transport by the terbium bis-phthalocyaninato complex characterized by two distinct temperature regimes, below and above 50 K, respectively.