“Electrically tunable spin valve effect in vertical van-der-Waals
magnetic tunnel junctions”

Dr. Suyong Jung
Interdisciplinary Materials Measurement Institute, KRISS

May. 14 (Fri.), 02:30 PM
Online seminar
https://kaist.zoom.us/j/87512814606
회의 ID: 875 1281 4606
암호: 816956

Abstract:
Magnetic tunnel junctions (MTJ) and ensuing spin-valve operations employing high and low magnetoresistance (MR) states have laid the foundations for many of commercial spintronic applications. Coping with the already established field, it is highly desirable to extend the conventional MTJ spin-valve functionality with an easily accessible device parameter. Here, we report experimental realizations of bias-voltage controlled MTJ spin-valve operations, in which high and low tunneling MR states can be selected without reconfiguring ferromagnet polarizations. Our vertical MTJs are prepared through all van der Waals (vdW)-coupled 2D–2D assemblies with Fe3GeTe2 (FGT) as spin-supplying and detecting ferromagnetic electrodes, and a semiconducting WSe2 as an electrically and physically stable tunnel barrier. We observe clear spin-valve characteristics with MR-switching ratios as high as ~ 110%. Quite interestingly, the high- and the low-MR states become reversed when a tunneling-bias voltage varies, and resulting negative MR switchings become as low as ~ – 40%. Based on density functional theory and quantum transport simulations, we verify that the bias-voltage induced spin-valve operations are directly attributed to the spin-polarized electronic structures, in particular, the concomitant contributions from the spin-polarized itinerant electrons and the localized spin states in the 2D metallic ferromagnet, FGT.