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

Gabureac, M.S., MacLaren, D.A. , Courtois, H. and Marrows, C.H. (2014) Long-ranged magnetic proximity effects in noble metal-doped cobalt probed with spin-dependent tunnelling. New Journal of Physics, 16(4), 043008. (doi: 10.1088/1367-2630/16/4/043008)

Abstract

We inserted non-magnetic layers of Au and Cu into sputtered AlO$_{x}$-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$_{x}$ 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 ~3nm, 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 ≤ 1nm, indicating that this is a sufficient quantity of Co to form a fully spin-polarized band structure at the interface with the tunnel barrier.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: MacLaren, Professor Donald
• Authors: Gabureac, M.S., MacLaren, D.A., Courtois, H., and Marrows, C.H.
• College/School: College of Science and Engineering > School of Physics and Astronomy
• Journal Name: New Journal of Physics
• Publisher: Institute of Physics Publishing Ltd.
• ISSN: 1367-2630
• ISSN (Online): 1367-2630
• Copyright Holders: Copyright © 2014 IOP Publishing Ltd and Deutsche Physikalische Gesellschaft
• First Published: First published in the New Journal of Physics 16(4):043008
• Publisher Policy: Reproduced under a Creative Commons License