Atomic-scale structural analyses of epitaxial Co∕Re superlattices

Abstract

High-resolution transmission electron microscopy and scanning transmission electron microscopy (STEM) have been used to investigate atomic-scale structural properties of Co∕Re trilayers and superlattices grown via magnetron sputtering. The sample growth was epitaxial with the (101¯0) plane of Co and Re parallel to the (112¯0) plane of Al2O3, and the [001] direction of Re and Co coinciding with that of the Al2O3. Both low-angle and high-angle Z-contrast STEM images show a very uniform layer thickness. However, the interface roughness between the Re and Co layers monotonically increases with interface distance from the substrate. These results strongly imply that, in the epitaxial Re∕Co superlattice system, interface roughness plays a more important role in the giant magnetoresistance effect than thickness fluctuations of the spacer layer. Previous anisotropic magnetoresistance measurements can be explained in terms of the observed atomic-scale structure.

Structural and compositional characterization of a Co∕Re multilayer and superlattice

“…We have demonstrated that atomic-scale structure of Co/ Re epitaxial SL could be realized by combining high-resolution transmission electron microscopy ͑TEM͒ and Z-contrast scanning transmission electron microscopy ͑STEM͒. 10 Epitaxial Co/ Re SLs exhibit both GMR and anisotropic magnetoresistance ͑AMR͒, where the GMR and AMR can either compete or reinforce one another. [11][12][13][14] In this paper, we report detailed structural and compositional characterizations of a Co/ Re trilayer and a 19-period SL via TEM/STEM imaging, as well as nanoscale electron energy loss spectroscopy ͑EELS͒ and energy dispersive x-ray ͑EDX͒ spectroscopy.…”