Preparation And Magnetic Properties Of Nickel Alloy Nanotubes/Wires

Times is advancing,society is developing,and information technology is also innovating.From initial punch cards to later magnetic tape storage as well as the current soft disc and hard disc,the technology and materials of memory are also constantly improving.In recent years,with the advent of nanotechnology,many nano-products have been manufactured,for example magnetic nanomaterial.In this paper,nickel alloy nanotubes/wires were prepared into anodic aluminum oxidation(AAO) templates by electrochemical method.First,the alumina template was obtained by two-step oxidation.The SEM image shows that the pore size of the template is uniform.Co₃Ni alloy nanowires were prepared by adjusting the deposition voltage and the ratio of cation concentration in electrolyte.The X-ray diffraction(XRD)patterns shows that when the deposition voltage is less than-0.9V or the ratio of Co and Ni concentration is greater than 1:19,the alloy of Co and Ni does not formed a crystalline phase;When the deposition voltage is-0.9V or the ratio of Co ions and Ni ions is 1:19,the crystal phase of Co₃Ni is formed,which has a face-centered cubic structure with a (111)preferred orientation.The morphology of Ni-Co alloy was observed by SEM,and it is found that the Ni-Co alloy is arranged very neatly,and the nanoalloys are nanowires rather than nanotubes because of the long deposition time.By analyzing the hysteresis loops,it is found that the coercivity and remanent magnetization of Co₃Ni nanowires are the largest.Because crystalline phase of Co₃Ni is formed under such deposition conditions,the magnetic properties of Co₃Ni nanowires are improved.Three kinds of permalloy,FeNi₃,Fe_1.85Ni_1.25 and Fe₂Ni,were obtained by adjusting the deposition voltage and the ratio of cation in the electrolyte.The XRD images of permalloy show that Fe_1.85Ni_1.25and Fe₂Ni are body-centered cubic structure,and they all grow preferentially along (220) direction;FeNi₃is face-centered cubic structure with preferred growth direction is (111).The SEM images show that the diameter of permalloy is very similar to that of alumina template,and there are no nanowires,and the nanotubes are neatly arranged.Through the comparison of the hysteresis loops of three kinds of permalloy,it is found that the remanent magnetization does not increase constantly,but first increases then decreases with increasing proportion of Ni ions in the solution.Among them,Fe₂Ni has the strongest remanent magnetization and the largest coercivity.Therefore,the trace doping of nickel can significantly change the magnetic properties of the permalloy.Finally,the micromagnetic simulation software of the Object Oriented Micro Magnetic Framework(OOMMF) was used to simulate the permalloy.By the method of controlling variables,the length and diameter of nanotubes were taken as variables,respectively.It is found that the magnetic properties of nanotubes change significantly with the change of nanotube length or diameter.The change of two variables would lead to the change of the shape of nanotubes,so magnetic properties of nanotubes would be changed too.In the process of magnetization reversal of nanotubes,the procession started from both ends,and the magnetization reversal core was formed at both ends of nanotubes,then moved slowly to the center of nanotubes.Finally,the reversal process had been completed,and the magnetization reversal core disappeared at the same time.