Overcoming the Efficiency-Stability Trade-off in Spin-Orbit Torque Devices with Thermally Robust BCC NiW Alloys
Abstract
The development of high-performance spin-orbit torque (SOT) magnetic memories is fundamentally constrained by a persistent trade-off between spin Hall efficiency, thermal structural stability, and perpendicular magnetic anisotropy in conventional heavy metals. Here, we overcome this limitation by engineering body-centered-cubic (BCC) Ni-doped W alloys as highly efficient and thermally robust spin-current sources. Ni30W70/CoFeB heterostructures achieve deterministic out-of-plane magnetization switching at an ultra-low critical current density of 1.78 MA/cm2, nearly threefold lower than that of β-W, while maintaining a high anisotropy field of 8,500 Oe and a thermal stability factor of 57.9. The BCC Ni30W70 alloy preserves its structural integrity and the perpendicular magnetic anisotropy of the adjacent CoFeB layer after annealing at 450 ∘C, demonstrating robustness under the stringent thermal processing conditions relevant to back-end-of-line integration. Harmonic Hall and ferromagnetic resonance measurements reveal a large spin Hall angle of -0.39 and a high interfacial spin transparency of 0.75, demonstrating efficient spin-current generation and interfacial transmission. First-principles calculations further reveal enhanced intrinsic spin Hall conductivity in W-rich BCC NiW alloys, associated with the Fermi level lying within a spin-orbit-coupling-induced band gap. These findings establish BCC NiW alloys as a scalable and thermally resilient material platform for energy-efficient SOT-MRAM.
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BibTeX
@misc{pan2026overcoming,
title = {{Overcoming the Efficiency-Stability Trade-off in Spin-Orbit Torque Devices with Thermally Robust BCC NiW Alloys}},
author = {Yu-Ming Pan and Chen-Yi Wei and Yi-Cheng Tsou and Tsung-Yu Pan and Guang-Yu Guo and Chih-Huang Lai},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.00623},
eprint = {2609.00623},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.00623},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Overcoming the Efficiency-Stability Trade-off in Spin-Orbit Torque Devices with Thermally Robust BCC NiW Alloys
AU - Yu-Ming Pan
AU - Chen-Yi Wei
AU - Yi-Cheng Tsou
AU - Tsung-Yu Pan
AU - Guang-Yu Guo
AU - Chih-Huang Lai
PY - 2026
DA - 2026/09/01
PB - arXiv
DO - 10.48550/arxiv.2609.00623
UR - https://arxiv.org/abs/2609.00623
AB - The development of high-performance spin-orbit torque (SOT) magnetic memories is fundamentally constrained by a persistent trade-off between spin Hall efficiency, thermal structural stability, and perpendicular magnetic anisotropy in conventional heavy metals. Here, we overcome this limitation by engineering body-centered-cubic (BCC) Ni-doped W alloys as highly efficient and thermally robust spin-current sources. Ni_30W_70/CoFeB heterostructures achieve deterministic out-of-plane magnetization switching at an ultra-low critical current density of 1.78 MA/cm^2, nearly threefold lower than that of β-W, while maintaining a high anisotropy field of 8,500 Oe and a thermal stability factor of 57.9. The BCC Ni_30W_70 alloy preserves its structural integrity and the perpendicular magnetic anisotropy of the adjacent CoFeB layer after annealing at 450 ^∘C, demonstrating robustness under the stringent thermal processing conditions relevant to back-end-of-line integration. Harmonic Hall and ferromagnetic resonance measurements reveal a large spin Hall angle of -0.39 and a high interfacial spin transparency of 0.75, demonstrating efficient spin-current generation and interfacial transmission. First-principles calculations further reveal enhanced intrinsic spin Hall conductivity in W-rich BCC NiW alloys, associated with the Fermi level lying within a spin-orbit-coupling-induced band gap. These findings establish BCC NiW alloys as a scalable and thermally resilient material platform for energy-efficient SOT-MRAM.
ER -