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

• Published in: arXiv.org 2014-04
• Main Authors: Gabureac, Mihai S, Mac Laren, Donald A, Courtois, Hervé, Marrows, Christopher M
• Format: Article
• Language: English
• Subjects: Copper; Dichroism; Electron microscopes; Gold; Magnetoresistance; Magnetoresistivity; Noble metals; Polarization (spin alignment); Seismic engineering; Thickness measurement; Transmission electron microscopy; Tunnel construction; Tunnel junctions
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.1404.6565

We inserted non-magnetic layers of Au and Cu into sputtered AlOx-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/AlOx 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 ~3 nm, implying that spin-polarized carriers penetrate the interface noble metal to dis- tances 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