Ultralow-Voltage Spin-Transfer Switching in Perpendicularly Magnetized Magnetic Tunnel Junctions with Synthetic Antiferromagnetic Reference Layer

We developed top-free-type perpendicularly magnetized magnetic tunnel junctions (p-MTJs) with a synthetic antiferromagnetic (SAF) bottom reference layer consisting of [Co/Pt] superlattice and Ru spacer layers. We successfully demonstrated practical properties such as a low resistance--area ($\mathit...

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Bibliographic Details
Published inApplied physics express Vol. 6; no. 11; pp. 113006 - 113006-4
Main Authors Yakushiji, Kay, Fukushima, Akio, Kubota, Hitoshi, Konoto, Makoto, Yuasa, Shinji
Format Journal Article
LanguageEnglish
Published The Japan Society of Applied Physics 01.11.2013
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Summary:We developed top-free-type perpendicularly magnetized magnetic tunnel junctions (p-MTJs) with a synthetic antiferromagnetic (SAF) bottom reference layer consisting of [Co/Pt] superlattice and Ru spacer layers. We successfully demonstrated practical properties such as a low resistance--area ($\mathit{RA}$) product (${<}3$ $\Omega$ μm 2 ), ultralow writing voltage (${<}200$ mV) for spin-transfer-torque (STT) switching, and high annealing stability (up to 350 °C) in the same p-MTJ cells. Moreover, the p-MTJs showed clear bi-stable states even at zero external magnetic fields, thanks to the low stray field from the SAF structure. The results are promising for both high integration and ultralow-voltage operation of STT magnetoresistive random access memory (MRAM).
Bibliography:Schematic stacking structure of p-MTJ with p-SAF reference layer (left side) and cross-sectional TEM image of p-MTJ (right side). Thick arrows represent typical magnetization configurations at zero magnetic field. Magnetization curves ($M$--$H$ loops) of unpatterned p-MTJ films after annealing at 280 °C (brown line) and 350 °C (green line). An external magnetic field ($H$) was applied perpendicularly to the plane. Insets represent magnetic configurations in the free layer and p-SAF reference layer. Annealing temperature ($T_{\text{a}}$) dependence of (a) MR ratio, (b) resistance--area ($\mathit{RA}$) product, and (c) anisotropy field ($H_{\text{k}}$) at room temperature for p-MTJs. Magnetization switching properties of p-MTJs. (a) Switching by magnetic field and (b) by STT. (c) Stochastic distribution of STT switching probability as a function of writing voltage. Thick vertical arrows represent magnetization configurations.
ISSN:1882-0778
1882-0786
DOI:10.7567/APEX.6.113006