Abstract
Part I Unusual ferromagnetism has been observed in high density free-standing CrSi2(core)/SiO2(shell) nanocables synthesized by atmosphere pressure chemical vapor deposition method without using any metal catalyst, which is in evident contrast to diamagnetic properties of both CrSi2 and SiO2 in bulk. The hexagonal CrSi2 C40 type (P6222) nanowires grows along [0001] direction and is covered with amorphous SiO2, as characterized by high resolution transmission electron microscopy (HRTEM). The supercell used in the first-principles calculation, which include the interface between CrSi2 and amorphous SiO2, was constructed from analyses of HRTEM images. The simulations results indicate that Cr atoms around the interface with an anomalously high magnetization up to about 2 μB/atom, due to distorted /dangling bonds, and are consistent with the magnetic measurements by also considering the roughness and distribution of oxygen around the interface. These results point towards a new way to tune magnetism in core/shell nanowires. Part II The underlying antiferromagnetic NiO was prepared using a dual ion beam deposition system. Dual ion beam deposition system contains DC ion source and RF ion source (assisted beam). Change the RF ion source bombardment voltage (VRF=50、75、100、150 and 200V) and the flow rate of oxygen (O2 flow rate=0.5、0.8 and 1 sccm and fixed Ar flow rate =2.5 sccm), to discuss these changes on the growth of NiO films. The surface roughness of NiO films were analyzed by atomic force microscopy, and the crystal structure of the NiO films were characterized with X-ray diffraction at a grazing angle of one degree. To understand whether the underlying growth of NiO films will influence the growth of Co/Pt multilayers and magnetic properties (perpendicular anisotropy and perpendicular exchange bias). The Co/Pt multilayers will prepare by electron beam evaporation system, however, the system has some problems not yet resolved, so these part need further study in the future.