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Falaication, magnetic properties, and electronic structures of nanoscale zinc-blende MnAs dots

纳米级闪锌矿MnAs点的断裂、磁性和电子结构

基本信息

批准号：
13554012
负责人：
ONO Kanta
金额：
$ 8.13万
依托单位：
High Energy Accelerator Research Organization (2003)The University of Tokyo (2001-2002)
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2003
项目状态：
已结题

项目摘要

NiAs-type Mn pnictide fibres grown on GaAs substrates by molecular-beam epitaxy (MBE) have been extensively studied because of their potential as spintronic device applications utilizing ferromagnetic metal-semiconductor hybrid structures. Among them MnAs and MnSb have a higher potential for spintronic devices due to their high Curie temperatures Tc (MnAs: Tc~320K, MnSb: Tc~600 K). Basic physical properties of MnAs films including the consecutive phase transitions between the NiAs-MnP-liAs type crystalline structures in the bulk have been investigated. The electronic structure of MBE-grown Mn pnictides films has also been investigated by photoemission spectroscopy including spin-resolved measurements.At first, ferromagnetic nanoscale zinc-blende MnAs dots were successfully fabricated on a sulfur-passivated GaAs (001) surface by molecular-beam epitaxy. Transmission electron microscopy and selected area electron diffraction showed that the crystalline structure was not the same as that of bulk MnAs with NiAs-type hexagonal crystalline structure, but of zinc-blende type. In in situ photoemission spectroscopy of the zinc-blende MnAs dots, the Fermi edge was not clearly observed and the Mn 3d partial density of states was similar to that of the diluted ferromagnetic semiconductor Gal-xMnxAs, which also supports the fabrication of zinc-Hende MnAs in the nanoscale.In the second step, we have synthesized Mn-Pt nanoparticles using a chemical preparation based on a liquid-phase reaction caused by decomposition of organometallic precursors. The synthesized monodisperse Mn52.5Pt47.5 nanoparticles show an fcc crystalline structure and ferromagnetic properties even at the room temperature. Mn52.5Pt47.5, which is not ferromagnetic in a bulk form, shows a completely different physical property in nanparticles.

GaAs衬底上生长的分子束外延（MBE）的砷化镓型锰磷属元素化物纤维已被广泛研究，因为它们的潜在的自旋电子器件的应用，利用铁磁金属-半导体混合结构。其中MnAs和MnSb由于其高居里温度Tc（MnAs：Tc~ 320 K，MnSb：Tc~600 K）而具有更高的自旋电子器件的潜力。研究了MnAs薄膜的基本物理性质，包括体材料中NiAs-MnP-LiAs型晶体结构之间的连续相变。首先，利用分子束外延技术在硫钝化的GaAs（001）表面上成功地制备了铁磁纳米级锌掺杂MnAs点。透射电子显微镜和选区电子衍射表明，其晶体结构与块体MnAs的NiAs型六方晶体结构不同，而是闪锌矿型。在原位光电子能谱中，未观察到明显的费米边，Mn的3d偏态密度与稀释铁磁半导体Ga 1-xMn xAs的相似，这也支持了纳米尺度的Zn Hende MnAs的制备。我们已经使用基于由有机金属前体的分解引起的液相反应的化学制备合成了Mn-Pt纳米颗粒。所合成的单分散Mn52.5Pt47.5纳米颗粒即使在室温下也显示出fcc晶体结构和铁磁性能。Mn52.5Pt47.5在块状形式下不是铁磁性的，在纳米颗粒中显示出完全不同的物理性质。