Long-ranged magnetic proximity effects in noble metal-doped cobalt probed with spin-dependent tunnelling

We inserted non-magnetic layers of Au and Cu into sputtered AlO -based magnetic tunnel junctions and Meservey-Tedrow junctions in order to study their effect on tunnelling magnetoresistance (TMR) and spin polarization (TSP). When either Au or Cu are inserted into a Co/AlO interface, we find that TMR...

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Bibliographic Details
Published in:New journal of physics 2014-04, Vol.16 (4), p.43008-17
Main Authors: Gabureac, M S, MacLaren, D A, Courtois, H, Marrows, C H
Format: Article
Language:English
Subjects:
72.25.-b
75.47.-m
Condensed Matter
Copper
Decay
Dichroism
Electron microscopes
Gold
magnetic proximity
magnetic tunnel junction
Magnetoresistance
Magnetoresistivity
Nanostructure
Noble metals
Physics
Polarization (spin alignment)
Seismic engineering
spin polarization
spintronics
Superconductivity
Thickness measurement
Tunnel construction
Tunnel junctions
Tunnelling
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Summary:We inserted non-magnetic layers of Au and Cu into sputtered AlO -based magnetic tunnel junctions and Meservey-Tedrow junctions in order to study their effect on tunnelling magnetoresistance (TMR) and spin polarization (TSP). When either Au or Cu are inserted into a Co/AlO interface, we find that TMR and TSP remain finite and measurable for thicknesses up to several nanometres. High-resolution transmission electron microscopy shows that the Cu and Au interface layers are fully continuous when their thickness exceeds , implying that spin-polarized carriers penetrate the interface noble metal to distances exceeding this value. A power law model based on exchange scattering is found to fit the data better than a phenomenological exponential decay. The discrepancy between these length scales and the much shorter ones reported from x-ray magnetic circular dichroism studies of magnetic proximitization is ascribed to the fact that our tunnelling transport measurements selectively probe s-like electrons close to the Fermi level. When a 0.1 nm thick Cu or Au layer is inserted within the Co, we find that the suppression of TMR and TSP is restored on a length scale of , indicating that this is a sufficient quantity of Co to form a fully spin-polarized band structure at the interface with the tunnel barrier.
ISSN:1367-2630
1367-2630
DOI:10.1088/1367-2630/16/4/043008