Direct evidence for minority spin gap in the Co2MnSi Heusler alloy

Stéphane Andrieu (1) , Amina Neggache (1) , Thomas Hauet (1) , Thibaut Devolder (2) , Ali Hallal (3) , Mairbek Chschiev (3) , Alexandre Bataille (4) , Patrick Le Fevre (5) , Francois Bertran (5)

1 IJL - Institut Jean Lamour
2 Institut d'Electronique Fondamentale
3 SPINTEC - SPINtronique et TEchnologie des Composants
4 CEA - Commissariat à l'énergie atomique et aux énergies alternatives
5 SSOLEIL - Synchrotron SOLEIL

Half Metal Magnets are of great interest in the field of spintronics because of their potential full spin-polarization at the Fermi level and low magnetization damping. The high Curie temperature and predicted 0.7eV minority spin gap make the Heusler alloy Co2MnSi very promising for applications.We investigated the half-metallic magnetic character of this alloy using spin-resolved photoemission, ab initio calculation and ferromagnetic resonance. At the surface of Co2MnSi, a gap in the minority spin channel is observed, leading to 100% spin polarization. However, this gap is 0.3 eV below the Fermi level and a minority spin state is observed at the Fermi level. We show that a minority spin gap at the Fermi energy can nevertheless be recovered either by changing the stoichiometry of the alloy or by covering the surface by Mn, MnSi or MgO. This results in extremely small damping coefficients reaching values as low as 7x 10-4.

Mots clés: Co2MnSi; molecular beam epitaxy; spin resolved photoemission; spintronic; Half Metal Magnet; Heusler alloys

Domaines: Science des matériaux [cond-mat.mtrl-sci]

Stéphane Andrieu, Amina Neggache, Thomas Hauet, Thibaut Devolder, Ali Hallal, et al.. Direct evidence for minority spin gap in the Co2MnSi Heusler alloy. 2015. ⟨hal-01216716v1⟩