Physical property of two components nono-crystals prepared with GDM

本课题研究了多元素组成的纳米晶体。采用气相冷凝沉积法（GDM）对两种不同的工艺进行了改进，得到了两种组分的纳米晶体。此外，还报道了用简单GDM制备的单元素纳米晶体的基本性质。作为多元素纳米晶体体系的基础，研究了GDM镍纳米晶体的磁性。沉积膜由直径约9 nm的细颗粒组成。热退火至400℃时晶粒尺寸增大约20 nm。纳米晶体的矫顽力随晶粒尺寸小于13nm的- 6次幂而变化。这可以用随机各向异性模型来解释。有效的局部磁各向异性为1.9 ~ 3.5 × 104 J/ m3，是体镍的2 ~ 5倍。从磁场冷磁化测量中，未观察到交换各向异性引起的Hc位移。晶粒周围氧化产生的反铁磁层似乎不是各向异性的原因。通过混合来自两个独立源的超细颗粒流，制备了含铁磁性金属（Fe和Co）的两组分纳米晶体。在细颗粒混合在基材上的情况下，成分在大范围内被调制，这意味着流动不能以这种方式很好地混合。接下来，我们在传输管中混合了流动，调制得到了改进，然而，在混合光束的每个痕迹中都发现了元素的明显分离。另一种改进GDM的技术，将细颗粒与衬底上的其他溅射金属混合，已经过测试以实现颗粒材料。通过这种方法，与以前的方法相比，混合效果明显改善。在Co-Ag体系中，GMR是预期的，但只发现了小的磁电阻。这可能归因于Co颗粒的大小，并计划进一步研究。少

In this research project, nano-crystals composed of multi-elements were investigated. 2 different techniques, which are modified from Gas condensation and Deposition Method (GDM), were tested to realize 2 components nano-crystals. Additionally, basic properties of single element nanocrystals produced by the simple GDM are also reported.As basics of the multi-element nano-crystal system, magnetism of GDM Ni nano-crystals was investigated. As deposited films were composed of fine particles with approximately 9 nm in diameter. Thermal annealing up to 400°C increased the grain size of around 20 nm. Coercive forces of the nano-crystals vary in accordance with the - 6 powers of grain size smaller than 13nm. This is explained by the Random Anisotropy Model. Effective local magnetic anisotropy is deduced to be 1.9-3.5 x 104 J/ m3 and this magnitude is 2-5 times larger than that of bulk Ni. From the field cool magnetization measurement, Hc shift due to exchange anisotropy was not observed. The … More antiferromagnetic layer around grains originated from oxidation seems not to be responsible for the anisotropy.Two components nano-crystals including ferromagnetic metals such as Fe and Co were fabricated by mixing ultrafine particle flows from two individual sources. In the case where fine particles were mixed on a substrate, the composition was modulated in a large scale and this means flows do not mix well in this way. Next, we mixed the flows in the transfer tube and the modulation was improved, however, clear separation of the elements was found in an each trace of a mixed beam. Another technique modifying GDM, where fine particles were mixed with other sputtered metals on the substrate, has been tested to realize granular materials. By this way the mixing was remarkably improved compared with former ways. GMR was expected in a case of Co-Ag system, however only small magneto-resistance was found. This may be attributed to the size of Co particles and further investigation is planned. Less