Nature Commun. 4, 2425 (2013)

In molecular spintronics, magnetic molecules are interfaced with metallic electrodes to measure their spin state. Accessing electrons in spin-polarized states, such as 4f states, can, however, be difficult when those states lie far away from the Fermi level and do not contribute to charge transport, which is the case for molecules that include late lanthanides. Moreover, the orbital hybridization between molecular and electrode states can affect the magnetic properties of the molecule, to the extent that its magnetic moment can be quenched. Nicolae Atodiresei, Claire Besson and colleagues at ForschungszentrumJülich and RWTH Aachen University have now studied a molecule–electrode model system in which spin-polarized 4f states can be accessed by using a scanning tunnelling microscope and the magnetic moment of the molecule can be retained.

The researchers measure the density of states of a single bis(phthalocyaninato)-neodymium(III) (NdPc2) molecule adsorbed on a Cu(100) surface using scanning tunnelling spectroscopy. The three 4f electrons of neodymium are less localized than the 4f electrons in late lanthanides, and have a higher degree of hybridization with the Pc ligands. Moreover, they are all in the same spin channel, resulting in a net magnetic moment. By using the tip of the microscope to take spectra at different positions above the molecule — above the centre and above the Pc ligand — and by comparing the obtained spectra with ab initio calculations, the researchers conclude that the 4f states contribute to the tunnelling current and carry a magnetic moment.