Fe$_{4-x}$Co$_{x}$N薄膜的磁致伸缩性质：实验与第一性原理计算的见解
Magnetostrictive properties in Fe$_{4-x}$Co$_{x}$N films: Insight from experiments and first-principles calculations
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中文总结 AI 辅助
本研究结合实验与第一性原理计算，系统研究了宽组分范围内Fe4-xCoxN薄膜的磁致伸缩性质，发现λ111在x≈0.9时达最大+82 ppm，而λ100表现出巨大可调性和符号反转，为氮化物自旋电子器件设计提供了关键磁弹性参数。
中文摘要 AI 辅助
铁磁性氮化物Fe$_{4}$N因其高自旋极化率和大的磁致伸缩而受到自旋电子器件应用的关注。我们提出了一个结合实验和理论的研究，涵盖了宽组分范围内Fe$_{4-x}$Co$_{x}$N薄膜的磁致伸缩。Fe$_{4-x}$Co$_{x}$N薄膜通过分子束外延生长在SrTiO$_{3}$(001)衬底上，并使用光学悬臂法精确评估了沿[100]方向（${\lambda}$$_{100}$）和[111]方向（${\lambda}$$_{111}$）的磁致伸缩常数。实验结果表明，${\lambda}$$_{111}$在整个组分范围内保持正值，并在x≈0.9时达到最大值+82 ppm。${\lambda}$$_{111}$随x的变化远小于${\lambda}$$_{100}$的变化，后者表现出巨大的可调性和符号反转。第一性原理计算在x≥1.6时与实验${\lambda}$$_{111}$合理吻合，但在较低x时给出负值，并且在x=0.8时获得异常大的负${\lambda}$$_{111}$，此时费米能级与态密度中显著的少数自旋峰重合。计算得到的${\lambda}$$_{111}$强烈依赖于展宽参数，表明菱面体磁致伸缩对原子无序的处理高度敏感。由${\lambda}$$_{100}$和${\lambda}$$_{111}$导出的饱和磁致伸缩常数（${\lambda}$$_{s}$）也与(001)取向的多晶Fe$_{4-x}$Co$_{x}$N薄膜所测量的${\lambda}$$_{s}$进行了比较，并讨论了两者之间偏差的可能情景。我们的发现阐明了Fe$_{4-x}$Co$_{x}$N体系中磁致伸缩的基本特征，为设计基于氮化物的自旋电子器件提供了必要的磁弹性参数。
英文摘要
The ferromagnetic nitride Fe$_{4}$N has attracted attention for application in spintronic devices due to its high spin polarization and large magnetostriction. We present a combined experimental and theoretical study on the magnetostriction of Fe$_{4-x}$Co$_{x}$N films across a wide composition range. The Fe$_{4-x}$Co$_{x}$N films were grown on SrTiO$_{3}$(001) substrates using molecular beam epitaxy, and the magnetostriction constants along the [100] direction ($λ$$_{100}$) and [111] direction ($λ$$_{111}$) were precisely evaluated using an optical cantilever method. The experimental results reveal that $λ$$_{111}$ remains positive in the whole composition range and shows a maximum value of +82 ppm around x = 0.9. The variation in $λ$$_{111}$ with x is much smaller than that in $λ$$_{100}$, for which giant tunability and sign reversal are observed. First-principles calculations show reasonable agreement with the experimental $λ$$_{111}$ for x ${\ge}$ 1.6, but give negative values at lower x, and an exceptionally large negative $λ$$_{111}$ is obtained at x = 0.8, where the Fermi level coincides with a pronounced minority-spin peak in the density of states. The calculated $λ$$_{111}$ depends strongly on the smearing parameter, indicating that the rhombohedral magnetostriction is highly sensitive to the treatment of atomic disorder. The saturation magnetostriction constant ($λ$$_{s}$) derived from $λ$$_{100}$ and $λ$$_{111}$ is also compared with the $λ$$_{s}$ measured for the (001)-oriented polycrystalline Fe$_{4-x}$Co$_{x}$N films, and a possible scenario for deviation between them is discussed. Our findings clarify the basic features of magnetostriction in the Fe$_{4-x}$Co$_{x}$N system, providing essential magnetoelastic parameters for designing nitride-based spintronic devices.
发表机构
- Tohoku University（东北大学）
- Japan Atomic Energy Agency（日本原子能机构）
- National Institute for Materials Science（国立材料研究所）
- Kyoto Institute of Technology（京都工艺纤维大学）
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