Almeida Trevor P, Lequeux Steven, Palomino Alvaro, Sousa Ricardo C, Fruchart Olivier, Prejbeanu Ioan-Lucian, Dieny Bernard, Masseboeuf Aurélien, Cooper David
University of Grenoble Alpes, CEA, Leti, F-38000 Grenoble, France.
SUPA, School of Physics and Astronomy, University of Glasgow, Glascow G12 8QQ, United Kingdom.
Nano Lett. 2022 May 25;22(10):4000-4005. doi: 10.1021/acs.nanolett.2c00597. Epub 2022 May 16.
Perpendicular shape anisotropy (PSA) offers a practical solution to downscale spin-transfer torque magnetoresistive random-access memory (STT-MRAM) beyond the sub-20 nm technology node while retaining thermal stability. However, our understanding of the thermomagnetic behavior of PSA-STT-MRAM is often indirect, relying on magnetoresistance measurements and micromagnetic modeling. Here, the magnetism of a NiFe PSA-STT-MRAM nanopillar is investigated using off-axis electron holography, providing spatially resolved magnetic information as a function of temperature. Magnetic induction maps reveal the micromagnetic configuration of the NiFe storage layer (∼60 nm high, ≤20 nm diameter), confirming the PSA induced by its 3:1 aspect ratio. heating demonstrates that the PSA of the storage layer is maintained up to at least 250 °C, and direct quantitative measurements reveal a moderate decrease of magnetic induction. Hence, this study shows explicitly that PSA provides significant stability in STT-MRAM applications that require reliable performance over a range of operating temperatures.
垂直形状各向异性（PSA）为在低于20纳米技术节点的情况下缩小自旋转移矩磁阻随机存取存储器（STT-MRAM）规模提供了一种切实可行的解决方案，同时保持热稳定性。然而，我们对PSA-STT-MRAM热磁行为的理解往往是间接的，依赖于磁阻测量和微磁建模。在此，利用离轴电子全息术研究了NiFe PSA-STT-MRAM纳米柱的磁性，提供了作为温度函数的空间分辨磁信息。磁感应图揭示了NiFe存储层（约60纳米高，直径≤20纳米）的微磁结构，证实了由其3:1的纵横比引起的PSA。加热表明存储层的PSA至少在250°C时仍能保持，直接定量测量显示磁感应有适度下降。因此，本研究明确表明，PSA在需要在一系列工作温度下具有可靠性能的STT-MRAM应用中提供了显著的稳定性。
