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

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

doi:10.1103/PhysRevApplied.16.054052

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

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

Electronic Engineering

Research output: Contribution to journal › Article › peer-review

Abstract

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.

Original language	English
Article number	054052
Number of pages	10
Journal	Physical Review Applied
Volume	16
Issue number	5
DOIs	https://doi.org/10.1103/PhysRevApplied.16.054052
Publication status	Published - 30 Nov 2021

Bibliographical note

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10.1103/PhysRevApplied.16.054052

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Cite this

Elphick, K., Yoshida, K., Roy, T., Ichinose, T., Kunimatsu, K., Tsuchiya, T., Suzuki, K., Tsujikawa, M., Nagai, Y., Mizukami, S., Shirai, M., & Hirohata, A. (2021). Lattice Softening in Metastable bcc CoxMn100-x (001) Ferromagnetic Layers for a Strain-Free Magnetic Tunnel Junction. Physical Review Applied, 16(5), Article 054052. https://doi.org/10.1103/PhysRevApplied.16.054052

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abstract = "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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AU - Ichinose, Tomohiro

AU - Kunimatsu, Kazuma

AU - Tsuchiya, Tomoki

AU - Suzuki, Kazuya

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AU - Mizukami, Shigemi

AU - Shirai, Masafumi

AU - Hirohata, Atsufumi

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N2 - 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.

AB - 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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