Spin-polarized charge transfer between a ferromagnet and a molecule can promote molecular ferromagnetism 1, 2 and hybridized interfacial states3, 4. Observations of high spin-polarization of Fermi level states at room temperature5 designate such interfaces as a very promising candidate toward achieving a highly spin-polarized, nanoscale current source at room temperature, when compared to other solutions such as half-metallic systems and solid-state tunnelling over the past decades. We will discuss three aspects of this research. 1) Does the ferromagnet/molecule interface, also called an organic spinterface, exhibit this high spin-polarization as a generic feature? Spin-polarized photoemission experiments reveal that a high spin-polarization of electronics states at the Fermi level also exist at the simple interface between ferromagnetic cobalt and amorphous carbon6. Furthermore, this effect is general to an array of ferromagnetic and molecular candidates7. 2) Integrating molecules with intrinsic properties (e.g. spin crossover molecules) into a spinterface toward enhanced functionality requires lowering the charge transfer onto the molecule8 while magnetizing it1,2. We propose to achieve this by utilizing interlayer exchange coupling within a more advanced organic spinterface architecture. We present results at room temperature across the fcc Co(001)/Cu/manganese phthalocyanine (MnPc) system9. 3) Finally, we discuss how the Co/MnPc spinterface’s ferromagnetism stabilizes antiferromagnetic ordering at room temperature onto subsequent molecules away from the spinterface, which in turn can exchange bias the Co layer at low temperature10. Consequences include tunnelling anisotropic magnetoresistance across a CoPc tunnel barrier11. This augurs new possibilities to transmit spin information across organic semiconductors using spin flip excitations12.
Toward the design of large-scale electronic circuits that are entirely spintronics-driven, organic semiconductors
have been identified as a promising medium to transport information using the electron spin. This requires a
ferromagnetic metal-organic interface that is highly spin-polarized at and beyond room temperature, but this key building
block is still lacking. We show how the interface between Co and phthalocyanine molecules constitutes a promising
candidate. In fact, spin-polarized direct and inverse photoemission experiments reveal a high degree of spin polarization
at room temperature at this interface.
Fe films grown on Ag(001) as well as MgO films on Fe(001) have been studied by spin-polarized electron
reflection experiments. The three central observations are: 1) Oscillations with monolayer periodicity of the electron-spin
motion angles ε and Φ are observed as a function of the Fe thickness. They are attributed to the oscillatory behavior of
the surface-lattice strain that is relaxed at island edges of the incompletely filled top Fe layer. 2) For strongly relaxed
thick Fe films a giant spin precession angle of 180o, which is accompanied by a pronounced minimum in the reflected
electron intensity, is observed for an electron energy of 7.3 eV. 3) For the interface system MgO/Fe(001) a very strong
sensitivity of the spin motion angles on the MgO coverage is observed for certain energy ranges.
Ab-initio band structure and spin-dependent electron reflection calculations reveal that lattice relaxations during
growth of Fe on Ag(001) as well as MgO on Fe(001) are responsible for the strong changes of the electron-spin motion
We report on spin-polarized electron reflection experiments on Fe films on Ag(001). Upon reflecting from the Fe film
the electron-spin polarization is found to vary in an oscillatory fashion as a function of the Fe thickness. Two different
periods are identified. While the long period is related to the occurrence of quantum-size effects in the Fe layer, the short
period of one monolayer is attributed to the periodic variations of the film morphology alternating between filled and
incompletely filled atomic layers. This shows - because of total angular momentum conservation - that the transfer of
spin-angular momentum from the incident electrons to the ferromagnetic film can be extremely sensitive to the
morphology and structure of the film.
Electrons with the spin polarization vector perpendicular to the magnetization direction are spin analyzed after reflection at a ferromagnetic surface. The spin polarization precesses around the magnetization and simultaneously the angle between spin polarization and magnetization is changed. This spin motion is explained by the existence of a gap in the electronic band structure of the ferromagnet.