Research of the nano-structure of magnets by molecular dynamics simulation and deposition parameter variation sputtering method

近年来，在由交变磁层和非磁层组成的超晶格中发现了巨磁电阻效应。由于在高灵敏度磁阻磁头上的应用，超晶格的GMR受到了广泛的关注。GMR效应对超晶格界面结构和沉积参数非常敏感，但GMR与界面结构之间的关系尚不清楚。本研究的目的是通过分子动力学模拟膜的形成过程，在纳米尺度上阐明界面结构及其与沉积参数的关系。1998年，为了弄清溅射过程中沉积参数对Co/Cu超晶格结构的影响，对Co/Cu超晶格进行了分子动力学模拟。结果表明：1)对于相对于蒸发法的入射原子动能较低的情况，认为在岛状生长模式下，表面粗糙度的存在可能导致了针孔的形成。这可能是由于针孔破坏了钴层之间的反铁磁耦合，导致磁阻比较低。2)对于离子束溅射法对应的高动能入射原子，观察到界面处的相互扩散。3)界面处的互扩散量与入射角和原子的入射能量密切相关。在原子入射能量相同的情况下，随着原子入射角的增大，表面的相互扩散量减小。表面结构的模拟结果与先前报道的采用沉积参数变化溅射法（在溅射过程中改变氩气压力）制备表面纳米结构的实验结果吻合良好（A.Tsukamoto, et. al， J.Magn.）。Soc。日本。， Vol. 20.114(1996) 349.)。分子动力学模拟有助于了解上述磁体的纳米结构。少

Recently, a giant magnetoresistance (GMR) effect was observed in superlattices comprised of alternating magnetic and nonmagnetic layers. Much attention has been devoted to the GMR of superlattices because of the application for high sensitive magnetoresistive heads. The GMR effect is very sensitive to the structure atthe interface of superlattices and the deposition parameter, however, the relationships between GMR and interface structure is still not clear.The purpose of this research is clarifying the structure of the interface at the nanoscopic scale and relationships between those structure and deposition parameter by using molecular dynamics simulations of film formation process.In 1998, for the purpose of clarifying the effect of the deposition parameters in sputtering on the structure of Co/Cu super lattices, molecular dynamics simulations have been performed for Co/Cu super lattices. The results as follows :1)For the case of low kinetic energies of incident atoms corresponding … More to evaporation method, it is suggested that the formation of pinholes might been caused because of the existence of roughness at surface in island growth mode.This may cause the low values of the magnetoresistance ratio because that the pinholes broken the anti-ferromagnetic coupling between Co layers.2)For the case of high kinetic energies of incident atoms corresponding to Ion-beam sputtering method, the interdiffusion at the interface is observed.3)The amount of interdiffusion at the interface strongly depend on the angle of incidence and the incident energy of atoms. At same incident energy of atoms, the amount of interdiffusion at the surface decrease with increasing the angle of incidence of atoms.The simulated results of the structure at the surface is good agreement with the previously reported experimental results of fabrication of nano-structure at surface by deposition parameter variation sputtering method (Ar gas pressure was varied during sputtering) (A.Tsukamoto, et. al, J.Magn. Soc. Jpn., Vol. 20.114 (1996) 349.). The molecular dynamics simulation is useful to know the nano-structure of magnets as mentioned above. Less