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Giant room-temperature magnetoresistance in single-crystal Fe/MgO/Fe magnetic tunnel junctions


The tunnel magnetoresistance (TMR) effect in magnetic tunnel junctions (MTJs)1,2 is the key to developing magnetoresistive random-access-memory (MRAM), magnetic sensors and novel programmable logic devices3,4,5. Conventional MTJs with an amorphous aluminium oxide tunnel barrier, which have been extensively studied for device applications, exhibit a magnetoresistance ratio up to 70% at room temperature6. This low magnetoresistance seriously limits the feasibility of spintronics devices. Here, we report a giant MR ratio up to 180% at room temperature in single-crystal Fe/MgO/Fe MTJs. The origin of this enormous TMR effect is coherent spin-polarized tunnelling, where the symmetry of electron wave functions plays an important role. Moreover, we observed that their tunnel magnetoresistance oscillates as a function of tunnel barrier thickness, indicating that coherency of wave functions is conserved across the tunnel barrier. The coherent TMR effect is a key to making spintronic devices with novel quantum-mechanical functions, and to developing gigabit-scale MRAM.

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Figure 1: TEM images of a single-crystal MTJ with the Fe(001)/MgO(001)(1.8 nm)/Fe(001) structure.
Figure 2: Tunnel magnetoresistance of Fe(001)/MgO(001)/Fe(001) junctions.
Figure 3: Bias voltage—dependence of the TMR effect.


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We would like to thank M. Yamamoto, T. Katayama and Y. Yokoyama for their assistance with the experiments, and C. M. Boubeta, E. Tamura and H. Itoh for their helpful discussions.

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Correspondence to Shinji Yuasa.

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Yuasa, S., Nagahama, T., Fukushima, A. et al. Giant room-temperature magnetoresistance in single-crystal Fe/MgO/Fe magnetic tunnel junctions. Nature Mater 3, 868–871 (2004).

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