Voltage-Control Spintronics Memory With a Self-Aligned Heavy-Metal Electrode

Abstract

Voltage-control spintronics memory (VoCSM) is a spintronics-based memory that uses the voltage-control-magnetic-anisotropy (VCMA) effect as a selection method and the spin-Hall effect as a write method, and is a candidate for future nonvolatile main memory because of its advantages such as high density, low energy consumption, and robustness against read disturbance. In this paper, we demonstrate VoCSM with a self-aligned heavy-metal electrode, which is the most desirable in mass production and can expect the lowest critical current ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$I_{C})$ </tex-math></inline-formula> due to its narrow electrode structure. We obtain the value of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$I_{C}$ </tex-math></inline-formula> of around <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$400~\mu \text{A}$ </tex-math></inline-formula> for a magnetic tunnel junction of size <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$35~{\mathrm{ nm}} \times 245$ </tex-math></inline-formula> nm by using a self-aligned heavy-metal electrode. The value is lowered to one-third that of the conventional VoCSM structure and is comparable with that of spin-transfer torque writing. Moreover, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$I_{C}$ </tex-math></inline-formula> decreased due to the VCMA effect and reached <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$260~\mu \text{A}$ </tex-math></inline-formula> for <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{V}_{\mathrm {MTJ}} = -0.8$ </tex-math></inline-formula> V. We also found that the diffusion spin current from the lateral region, which is the concern matter of this structure, did not contribute very much to the switching due to the extremely short spin diffusion length of the heavy-metal electrode. It indicates that VoCSM with a self-aligned heavy-metal electrode may lead to the production of high-density and low-energy-consumption memory.