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

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 ∼3 nm, 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 ≲1 nm, indicating that this is a sufficient quantity of Co to form a fully spin-polarized band structure at the interface with the tunnel barrier.

Magnetic properties and field-driven dynamics of chiral domain walls in epitaxialPt/Co/AuxPt1−xtrilayers

“…So, when the electron beam goes through the TEM specimen, the thickness fluctuations of the thin layer will be added to the actual thickness resulting in the overestimation of thickness. It has also been reported previously than evaluating thickness from TEM crosssections might result in overestimated thicknesses, sometimes even two times higher than the real value 25 . Hence, x-ray reflectivity patterns of samples were fitted using the GenX package 26 , which yielded thicknesses very close to the nominal ones for the Co layers.…”

Magnetic properties and field-driven dynamics of chiral domain walls in epitaxial Pt/Co/Au$_x$Pt$_{1-x}$ trilayers

“…So, when the electron beam goes through the TEM specimen, the thickness fluctuations of the thin layer will be added to the actual thickness resulting in the overestimation of thickness. It has also been reported previously than evaluating thickness from TEM crosssections might result in overestimated thicknesses, sometimes even two times higher than the real value 25 . Hence, x-ray reflectivity patterns of samples were fitted using the GenX package 26 , which yielded thicknesses very close to the nominal ones for the Co layers.…”

Engineering Magnetic Domain-Wall Structure in Permalloy Nanowires

“…3 region. However, apparent overlap of the distributions will also occur due to broadening of the scattered electron beam and (more importantly) because the data derive from a projection of a three-dimensionally-rough interface onto a two dimensional plane, as described elsewhere [24].…”

“…None of the layers have a "top-hat" profile and the tails of the distributions overlap, suggesting a degree of intermixing of Cr and Py even in the unirradiated region. However, apparent overlap of the distributions will also occur due to broadening of the scattered electron beam and (more importantly) because the data derive from a projection of a three-dimensionally-rough interface onto a two dimensional plane, as described elsewhere [24].…”