Staff directory Laura Fernández Sánchez

Publications

2017

• Electronic Structure of Titanylphthalocyanine Layers on Ag(111)

  Lerch A., Fernandez L., Ilyn M., Gastaldo M., Paradinas M., Valbuena M.A., Mugarza A., Ibrahim A.B.M., Sundermeyer J., Höfer U., Schiller F. Journal of Physical Chemistry C; 121 (45): 25353 - 25363. 2017. 10.1021/acs.jpcc.7b09147. IF: 4.536

  We have investigated the electronic structures of axially oxo functionalized titanylphthalocyanine (TiOPc) on Ag(111) by X-ray and ultraviolet photoelectron spectroscopies, two-photon photoemission, X-ray absorption spectroscopy, and X-ray magnetic circular dichroism. Furthermore, we use complementary data of TiOPc on graphite and planar copper phthalocyanine (CuPc) on Ag(111) for a comparative analysis. Both molecules adsorb on Ag(111) in a parallel orientation to the surface, for TiOPc with an oxygen-up configuration. The interaction of nitrogen and carbon atoms with the substrate is similar for both molecules, while the bonding of the titanium atom to Ag(111) in the monolayer is found to be slightly more pronounced than in the CuPc case. Ultraviolet photoemission spectroscopy reveals an occupation of the lowest unoccupied molecular orbital (LUMO) level in monolayer thick TiOPc on Ag(111) related to the interaction of the molecules and the silver substrate. This molecule-metal interaction also causes an upward shift of the Ag(111) Shockley state that is transformed into an unoccupied interface state with energies of 0.23 and 0.33 eV for the TiOPc monolayer and bilayer, respectively, at the Brillouin zone center. © 2017 American Chemical Society.

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2016

• High Temperature Ferromagnetism in a GdAg2 Monolayer

  Ormaza M., Fernández L., Ilyn M., Magana A., Xu B., Verstraete M.J., Gastaldo M., Valbuena M.A., Gargiani P., Mugarza A., Ayuela A., Vitali L., Blanco-Rey M., Schiller F., Ortega J.E. Nano Letters; 16 (7): 4230 - 4235. 2016. 10.1021/acs.nanolett.6b01197. IF: 13.779

  Materials that exhibit ferromagnetism, interfacial stability, and tunability are highly desired for the realization of emerging magnetoelectronic phenomena in heterostructures. Here we present the GdAg2 monolayer alloy, which possesses all such qualities. By combining X-ray absorption, Kerr effect, and angle-resolved photoemission with ab initio calculations, we have investigated the ferromagnetic nature of this class of Gd-based alloys. The Curie temperature can increase from 19 K in GdAu2 to a remarkably high 85 K in GdAg2. We find that the exchange coupling between Gd atoms is barely affected by their full coordination with noble metal atoms, and instead, magnetic coupling is effectively mediated by noble metal-Gd hybrid s,p-d bands. The direct comparison between isostructural GdAu2 and GdAg2 monolayers explains how the higher degree of surface confinement and electron occupation of such hybrid s,p-d bands promote the high Curie temperature in the latter. Finally, the chemical composition and structural robustness of the GdAg2 alloy has been demonstrated by interfacing them with organic semiconductors or magnetic nanodots. These results encourage systematic investigations of rare-earth/noble metal surface alloys and interfaces, in order to exploit them in magnetoelectronic applications. © 2016 American Chemical Society.

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