Abstract
Magnetic tunnel junctions (MTJs) with ferromagnetic electrodes possessing a perpendicular magnetic easy axis are of great interest as they have a potential for realizing next-generation high-density non-volatile memory and logic chips with high thermal stability and low critical current for current-induced magnetization switching1,2,3. To attain perpendicular anisotropy, a number of material systems have been explored as electrodes, which include rare-earth/transition-metal alloys4,5, L10-ordered (Co, Fe)–Pt alloys3,6,7 and Co/(Pd, Pt) multilayers1,8,9,10. However, none of them so far satisfy high thermal stability at reduced dimension, low-current current-induced magnetization switching and high tunnel magnetoresistance ratio all at the same time. Here, we use interfacial perpendicular anisotropy between the ferromagnetic electrodes and the tunnel barrier of the MTJ by employing the material combination of CoFeB–MgO, a system widely adopted to produce a giant tunnel magnetoresistance ratio in MTJs with in-plane anisotropy11,12,13. This approach requires no material other than those used in conventional in-plane-anisotropy MTJs. The perpendicular MTJs consisting of Ta/CoFeB/MgO/CoFeB/Ta show a high tunnel magnetoresistance ratio, over 120%, high thermal stability at dimension as low as 40 nm diameter and a low switching current of 49 μA.
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Acknowledgements
We thank I. Morita, T. Hirata, A. Fukunaga and S. Koike for their technical support as well as M. Shirai for discussion. The work was supported in part by the ‘High-performance low-power consumption spin devices and storage systems’ program under Research and Development for Next-Generation Information Technology of MEXT, by the Japan Society for the Promotion of Science (JSPS) through its ‘Funding program for world-leading innovative R & D on science and technology (FIRST program)’ and the GCOE program at Tohoku University.
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S.I. and H.O. planned and supervised the study. S.I., F.M. and H.O. wrote the manuscript. K. Mizunuma, K. Miura, H.Y. and H.D.G. prepared samples and fabricated devices. K. Mizunuma, M.E. and S.K. investigated magnetic characteristics. H.Y. measured FMR spectra. K. Miura and H.Y. investigated the electrical properties of MTJ devices. All authors analysed the data, discussed the result and commented on the manuscript.
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Ikeda, S., Miura, K., Yamamoto, H. et al. A perpendicular-anisotropy CoFeB–MgO magnetic tunnel junction. Nature Mater 9, 721–724 (2010). https://doi.org/10.1038/nmat2804
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DOI: https://doi.org/10.1038/nmat2804
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