Giant orbital moments are responsible for the anisotropic magnetoresistance of atomic contacts

Gabriel Autes (1) , Cyrille Barreteau (1) , Marie-Catherine Desjonquères (1) , Daniel Spanjaard (2) , Michel Viret (3)

1 SPCSI - Service de Physique et de Chimie des Surfaces et Interfaces
2 LPS - Laboratoire de Physique des Solides
3 SPEC - UMR3680 - Service de physique de l'état condensé

We study here, both experimentally and theoretically, the anisotropy of magnetoresistance in atomic contacts. Our measurements on iron break junctions reveal an abrupt and hysteretic switch between two conductance levels when a large applied field is continuously rotated. We show that this behaviour stems from the coexistence of two metastable electronic states which result from the anisotropy of electronic interactions responsible for the enhancement of orbital magnetization. In both states giant orbital moments appear on the low coordinated central atom in a realistic contact geometry. However they differ by their orientation, parallel or perpendicular, with respect to the axis of the contact. Our explanation is totally at variance with the usual model based on the band structure of a monatomic linear chain, which we argue cannot be applied to 3d ferromagnetic metals.

Mots clés: transport ballistique; magnetoresistance; contact atomique

Domaines: Autre [cond-mat.other]

Gabriel Autes, Cyrille Barreteau, Marie-Catherine Desjonquères, Daniel Spanjaard, Michel Viret. Giant orbital moments are responsible for the anisotropic magnetoresistance of atomic contacts. 2008. ⟨hal-00250537⟩