Dependence of the Growth Mode in Epitaxial FePt Films on Surface Free Energy
Dependence of the Growth Mode in Epitaxial FePt Films on Surface Free Energy
复制标题
外延 FePt 薄膜的生长模式对表面自由能的依赖性
DOI：
10.1021/acsami.0c22510
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发表时间：
2021
影响因子：
9.5
通讯作者：
Takahashi Yukiko K.
中科院分区：
文献类型：
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作者：
Suzuki Ippei;Kubo Shoichi;Sepehri-Amin Hosein;Takahashi Yukiko K.
L10有序FePt合金外延薄膜由于其大的垂直磁各向异性（PMA）而成为磁记录和自旋电子学应用中最重要的材料之一。生产这些所需的上级性能的关键在于控制薄膜的生长模式。此外，有必要区分晶格失配和表面自由能对生长模式的影响，因为它们具有很强的相关性。在这项研究中，FePt外延膜的生长模式的表面自由能的影响进行了研究，使用MgO，NiO，和MgON表面几乎相同的晶格常数，以排除晶格失配的影响。结果发现，生长模式可以从MgO上的三维（3D）岛模式调整到MgON和NiO上的更二维（2D）的模式。接触角测量结果表明，MgON和NiO显示出比MgO更大的表面自由能，表明生长模式的差异是由于它们更大的表面自由能。此外，MgON被发现诱导不仅作为FePt生长在SrTiO 3（STO），具有小的晶格失配的平坦表面，但也比STO/FePt更大的PMA。由于较大的晶格失配有利于在FePt膜中诱导较高的PMA，因此专门使用MgO衬底，但3D岛生长是必不可少的。这项工作表明，调整的表面自由能，使我们能够实现一个大的PMA和平坦的膜表面在MgO上的FePt外延膜。结果还表明，修改的表面自由能是适当的薄膜的柔性功能设计。
Epitaxial thin films of L10-ordered FePt alloys are one of the most important materials in magnetic recording and spintronics applications due to their large perpendicular magnetic anisotropy (PMA). The key to the production of these required superior properties lies in the control of the growth mode of the films. Further, it is necessary to distinguish between the effect of lattice mismatch and surface free energy on the growth mode because of their strong correlation. In this study, the effect of surface free energy on the growth mode of FePt epitaxial films was investigated using MgO, NiO, and MgON surfaces with almost the same lattice constant to exclude the effect of lattice mismatch. It was found that the growth mode can be tuned from a three-dimensional (3D) island mode on MgO to a more two-dimensional (2D)-like mode on MgON and NiO. Contact angle measurements revealed that MgON and NiO show larger surface free energy than MgO, indicating that the difference in the growth mode is due to their larger surface free energy. In addition, MgON was found to induce not only a flat surface as FePt grown on SrTiO3(STO), which has a small lattice mismatch, but also a larger PMA than that of STO/FePt. As larger lattice mismatch is favored to induce a higher PMA into the FePt films, MgO substrates are exclusively used, but 3D island growth is indispensable. This work demonstrates that tuning the surface free energy enables us to achieve a large PMA and flat film surface in FePt epitaxial films on MgO. The results also indicate that modifying the surface free energy is pertinent for the flexible functional design of thin films.