Sasaki Yuta, Hiramatsu Ryoya, Kota Yohei, Kubota Takahide, Sonobe Yoshiaki, Sakuma Akimasa, Takanashi Koki, Kasai Shinya, Takahashi Yukiko K
International Center for Young Scientists, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, 305-0047, Japan.
Department of Applied Physics, Tohoku University, Sendai, 980-8579, Japan.
Small. 2022 May;18(20):e2200378. doi: 10.1002/smll.202200378. Epub 2022 Apr 15.
A ferromagnetic metal nanolayer with a large perpendicular magnetic anisotropy, small saturation magnetization, and small magnetic damping constant is a crucial requirement for high-speed spintronic devices. Fabrication of these devices on Si/SiO amorphous substrates with polycrystalline structure is also strongly desired for the mass production industry. This study involves the investigation of sub-terahertz (THz) magnetization precessional motion in a newly developed material system consisting of Cu Sb-type MnAlGe and (Mn-Cr)AlGe films by means of an all-optical pump-probe method. These materials exhibit large perpendicular magnetic anisotropy in regions of a few nanometers in size. The pseudo-2D crystal structures are clearly observed in the high-resolution transmission electron microscopy (TEM) images for the film samples grown on thermally oxidized silicon substrates. The TEM images also show a partial substitution of Cr atoms for the Mn sites in MnAlGe. A magnetization precession frequency of 0.164 THz with a relatively small effective magnetic damping constant of 0.012 is obtained for (Mn-Cr)AlGe. Theoretical calculation infers that the modification of the total density of states by Cr substitution decreases the intrinsic magnetic damping constant of (Mn-Cr)AlGe.
对于高速自旋电子器件而言，具有大的垂直磁各向异性、小的饱和磁化强度和小的磁阻尼常数的铁磁金属纳米层是一项关键要求。对于大规模生产行业来说，在具有多晶结构的Si/SiO非晶衬底上制造这些器件也有着强烈需求。本研究通过全光泵浦-探测方法，对由Cu Sb型MnAlGe和(Mn-Cr)AlGe薄膜组成的新开发材料系统中的亚太赫兹（THz）磁化进动运动进行了研究。这些材料在几纳米大小的区域内表现出大的垂直磁各向异性。在热氧化硅衬底上生长的薄膜样品的高分辨率透射电子显微镜（TEM）图像中清晰地观察到了伪二维晶体结构。TEM图像还显示在MnAlGe中Cr原子部分替代了Mn位点。对于(Mn-Cr)AlGe，获得了0.164 THz的磁化进动频率以及相对较小的有效磁阻尼常数0.012。理论计算推断，Cr替代导致的态密度总量的改变降低了(Mn-Cr)AlGe的固有磁阻尼常数。
