Fabrication of magnetic tunnel junctions with a single-crystalline LiF tunnel barrier. (21st February 2018)

• Record Type: Journal Article
• Authors: Narayananellore, Sai Krishna; Doko, Naoki; Matsuo, Norihiro; Saito, Hidekazu; Yuasa, Shinji
• Is Part Of: Japanese journal of applied physics. Volume 56:Number 4(2017)Supplement
• Publication Date: 2018-02-21
• Subjects: Physics -- Periodicals; 621.05
• DOI: 10.7567/JJAP.57.04FN04
• Languages: English
• ISSNs: 0021-4922

Abstract

Abstract: We fabricated Fe/LiF/Fe magnetic tunnel junctions (MTJs) by molecular beam epitaxy on a MgO(001) substrate, where LiF is an insulating tunnel barrier with the same crystal structure as MgO (rock-salt type). Crystallographical studies such as transmission electron microscopy and nanobeam electron diffraction observations revealed that the LiF tunnel barrier is single-crystalline and has a LiF(001)[100] ∥ bottom Fe(001)[110] crystal orientation, which is constructed in the same manner as MgO(001) on Fe(001). Also, the in-plane lattice mismatch between the LiF tunnel barrier and the Fe bottom electrode was estimated to be small (about 0.5%). Despite such advantages for the tunnel barrier of the MTJ, the observed tunnel magnetoresistance (MR) ratio was low (∼6% at 20 K) and showed a significant decrease with increasing temperature (∼1% at room temperature). The results imply that indirect tunneling and/or thermally excited carriers in the LiF tunnel barrier, in which the current basically is not spin-polarized, play a major role in electrical transport in the MTJ.