Band dispersion and spin-polarisation on the (100) surfaces of Fe3O4 and La0.7Sr0.3MnO3: A step forward in the proof of half-metallicity

May 20 2011
Types d’événements
Séminaire SPCSI
Karol Hricovini
SPEC Bât 466 p.111 (1er ét.)
Configuration de la salle en séminaire ou réunion
30 places
Vidéo Projecteur
20/05/2011
from 11:00

The field of spintronics is concerned with the search for highly spin-polarized materials, such as transition metal oxide based half-metals. The electronic structure of transition metal oxides is not well understood yet because 3d electrons are strongly correlated and cannot be adequately described within a standard band theory framework. There is also a lack of experimental results proving the true half-metallic behaviour.

We present ARPES and SP-ARPES studies of monocrystalline Fe3O4(100) / MgO(100) and La0.7Sr0.3MnO3(100) / SrTiO3(100) films. The absence of the quasiparticle close to the Fermi energy observed for both systems disagrees with band calculations, but can be explained by strong electron-lattice coupling. This coupling modifies also the spin polarisation at the Fermi level. Simulations of the spectre taking into account the k broadening and initial-state lifetime broadening, have allowed us to reconcile the ARPES data with the bulk band structure calculated within the LDA+U framework. In particular, the spin-resolved data are consistent with the half-metallic nature of both oxides.

LPMS, Université de Cergy-Pontoise – LENSIS/SPCSI, CEA