Enhanced magnetoresistance by monoatomic roughness in epitaxial Fe/MgO/Fe tunnel junctions
Résumé
Interfacial effects on spin and symmetry filtering in single-crystal Fe(001)/MgO/Fe magnetic tunnel junctions are investigated with the insertion of a Fe monoatomic step at the bottom MgO interface. After annealing, the atomically flat bottom electrode is covered by a fractional part of a Fe monoatomic layer resulting in two-dimensional Fe islands that are separated for low coverages and percolated above around half a monolayer. The magnetotransport properties of the junctions are studied as a function of this Fe sublayer coverage that is varied from 0 to 1 monolayer. Surprisingly, the magnetoresistance ratio exhibits a maximum for a coverage around half a monolayer. Tunneling spectroscopy experiments performed at low temperature allow relating this result to the decrease of the contribution of the interfacial resonance state to the conductance of the junction.
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Enhanced magnetoresistance by monoatomic roughness in epitaxial FeMgOFe tunnel junctions-PhysRevB.91.174403.pdf (1011.09 Ko)
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