Realizing Room-Temperature Resonant Tunnel Magnetoresistance in Cr/Fe/MgAl2O4 Quasi-Quantum Well Structures

Qingyi Xiang, Hiroaki Sukegawa, Mohamed Belmoubarik, Muftah Al-Mahdawi, Thomas Scheike, Shinya Kasai, Yoshio Miura, Seiji Mitani

Research output: Contribution to journalArticle

Abstract

The quantum well (QW) realizes new functionalities due to the discrete electronic energy levels formed in the well-shaped potential. Magnetic tunnel junctions (MTJs) combined with a quasi-QW structure of Cr/ultrathin-Fe/MgAl2O4(001)/Fe, in which the Cr quasi-barrier layer confines Δ1 up-spin electrons to the Fe well, are prepared with perfectly lattice-matched interfaces and atomic layer number control. Resonant peaks are clearly observed in the differential conductance of the MTJs due to the formation of QWs. Furthermore, enhanced tunnel magnetoresistance (TMR) peaks at the resonant bias voltages are realized for the MTJs at room temperature, i.e., it is observed that TMR ratios at specific and even high bias-voltages (Vbias) are larger than zero-bias TMR ratios for the MTJs with odd Fe atomic layers, in contrast to the earlier experimental studies. In addition, a new finding in this study is unique sign changes in the temperature coefficient of resistance (TCR) depending on the Fe thickness and Vbias, which is interpreted as a signature of the QW formation of Δ1 symmetry electronic states. The present study suggests that the spin-dependent resonant tunneling via the QWs formed in Cr/ultrathin-Fe/MgAl2O4/Fe structures should open a new pathway to achieve a large TMR at practically high Vbias.

Original languageEnglish
Article number1901438
JournalAdvanced Science
Volume6
Issue number20
DOIs
Publication statusPublished - 2019 Oct 1

Keywords

  • coherent tunneling
  • quantum well
  • resonant tunneling
  • spinel
  • tunnel magnetoresistance

ASJC Scopus subject areas

  • Medicine (miscellaneous)
  • Chemical Engineering(all)
  • Biochemistry, Genetics and Molecular Biology (miscellaneous)
  • Materials Science(all)
  • Engineering(all)
  • Physics and Astronomy(all)

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    Xiang, Q., Sukegawa, H., Belmoubarik, M., Al-Mahdawi, M., Scheike, T., Kasai, S., Miura, Y., & Mitani, S. (2019). Realizing Room-Temperature Resonant Tunnel Magnetoresistance in Cr/Fe/MgAl2O4 Quasi-Quantum Well Structures. Advanced Science, 6(20), [1901438]. https://doi.org/10.1002/advs.201901438