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Lattice Softening in Metastable bcc CoxMn100-x (001) Ferromagnetic Layers for a Strain-Free Magnetic Tunnel Junction

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  • Kelvin Elphick
  • Kenta Yoshida
  • Tufan Roy
  • Tomohiro Ichinose
  • Kazuma Kunimatsu
  • Tomoki Tsuchiya
  • Kazuya Suzuki
  • Masahito Tsujikawa
  • Yasuyoshi Nagai
  • Shigemi Mizukami
  • Masafumi Shirai
  • Atsufumi Hirohata


Publication details

JournalPhysical Review Applied
DateAccepted/In press - 5 Nov 2021
DatePublished (current) - 30 Nov 2021
Issue number5
Number of pages10
Original languageEnglish


In spintronics, one of the long-standing questions is why the MgO-based magnetic tunnel junction (MTJ) is almost the only option for achieving a large tunneling magnetoresistance (TMR) ratio at room temperature, although this is not as large as the theoretical prediction. This study focuses on the development of an almost strain-free MTJ using metastable bcc CoxMn100-x (Co − Mn) ferromagnetic films. We investigate the degree of crystallization in MTJs consisting of Co-Mn/MgO/Co-Mn in relation to their TMR ratios. Cross-section high resolution transmission electron microscopy reveals that almost consistent lattice constants of these layers for 66≤x ≤83 with large TMR ratios of 229% at room temperature, confirming the soft nature of the Co-Mn layer with some dislocations at the MgO/Co75Mn25 interfaces. Ab initio calculations confirm the crystalline deformation stability across a broad compositional range in Co-Mn, proving the advantage of a strain-free interface for much larger TMR ratios.

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