title: Atomic-Scale Structure and Local Chemistry of CoFeB-MgO Magnetic Tunnel Junctions.
abstract: Magnetic tunnel junctions (MTJs) constitute a promising building block for future nonvolatile memories and logic circuits. Despite their pivotal role, spatially resolving and chemically identifying each individual stacking layer remains challenging due to spatially localized features that complicate characterizations limiting understanding of the physics of MTJs. Here, we combine advanced electron microscopy, spectroscopy, and first-principles calculations to obtain a direct structural and chemical imaging of the atomically confined layers in a CoFeB-MgO MTJ, and clarify atom diffusion and interface structures in the MTJ following annealing. The combined techniques demonstrate that B diffuses out of CoFeB electrodes into Ta interstitial sites rather than MgO after annealing, and CoFe bonds atomically to MgO grains with an epitaxial orientation relationship by forming Fe(Co)-O bonds, yet without incorporation of CoFe in MgO. These findings afford a comprehensive perspective on structure and chemistry of MTJs, helping to develop high-performance spintronic devices by atomistic design.
authors.affiliation: WPI Advanced Institute for Materials Research, Tohoku University , 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan.
authors.forename: Zhongchang
authors.initials: Z
authors.lastname: Wang
authors.affiliation: WPI Advanced Institute for Materials Research, Tohoku University , 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan.|Institute of Engineering Innovation, University of Tokyo , 2-11-16, Yayoi, Bunkyo-ku, Tokyo 113-8656, Japan.
authors.forename: Mitsuhiro
authors.initials: M
authors.lastname: Saito
authors.affiliation: WPI Advanced Institute for Materials Research, Tohoku University , 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan.|Department of Physics, University of York , Heslington, York YO10 5DD, United Kingdom.
authors.forename: Keith P
authors.initials: KP
authors.lastname: McKenna
authors.affiliation: Center for Spintronics Integrated Systems, Tohoku University , 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan.|Center for Innovative Integrated Electronic Systems, Tohoku University , 468-1 Aramaki, Aza, Aoba-ku, Sendai 980-8577, Japan.
authors.forename: Shunsuke
authors.initials: S
authors.lastname: Fukami
authors.affiliation: Center for Spintronics Integrated Systems, Tohoku University , 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan.|Center for Innovative Integrated Electronic Systems, Tohoku University , 468-1 Aramaki, Aza, Aoba-ku, Sendai 980-8577, Japan.
authors.forename: Hideo
authors.initials: H
authors.lastname: Sato
authors.affiliation: Center for Spintronics Integrated Systems, Tohoku University , 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan.|Center for Innovative Integrated Electronic Systems, Tohoku University , 468-1 Aramaki, Aza, Aoba-ku, Sendai 980-8577, Japan.|Laboratory for Nanoelectronics and Spintronics, Research Institute of Electrical Communication, Tohoku University , 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan.
authors.forename: Shoji
authors.initials: S
authors.lastname: Ikeda
authors.affiliation: WPI Advanced Institute for Materials Research, Tohoku University , 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan.|Center for Spintronics Integrated Systems, Tohoku University , 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan.|Center for Innovative Integrated Electronic Systems, Tohoku University , 468-1 Aramaki, Aza, Aoba-ku, Sendai 980-8577, Japan.|Laboratory for Nanoelectronics and Spintronics, Research Institute of Electrical Communication, Tohoku University , 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan.
authors.forename: Hideo
authors.initials: H
authors.lastname: Ohno
authors.affiliation: WPI Advanced Institute for Materials Research, Tohoku University , 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan.|Institute of Engineering Innovation, University of Tokyo , 2-11-16, Yayoi, Bunkyo-ku, Tokyo 113-8656, Japan.|Nanostructures Research Laboratory, Japan Fine Ceramics Center , 2-4-1 Mutsuno, Atsuta, Nagoya 456-8587, Japan.
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Ikuhara
keywords: CoFeB−MgO; atomic structure; local chemistry; magnetic tunnel junction; scanning transmission electron microscopy