Preparation And Magnetic Properties Of Cobalt Alloy Nanotubes/Wires

With the development of information technology and the continuous improvement of technology in magnetic recording and magnetic storage,magnetic recording materials have been developed rapidly.One-dimensional magnetic nanomaterials have broad prospects in the application of high density magnetic storage and recording.In this experiment,self-fabricated anodic aluminum oxide(AAO)was used as template for the preparation of pure Co,Co-Dy alloy and Co-Cu multilayer nanowires/nanotubes by electrochemical deposition.X-ray diffraction(XRD),scanning electron microscopy(SEM)and energy dispersive spectrometer(EDS)were used to analyze and characterize the crystal structures,microstructures and elemental compositions of samples.The results show that,for Co-Dy alloy nanotubes,the content of Co in the samples increases with the decrease of the deposition voltage(-0.9 V,-1.0 V,-1.1 V).For the Co-Cu multilayer nanotubes/nanowires,the thickness of the Co and Cu layers are adjusted by setting different deposition times.The longer the deposition time is,the longer the thickness of each layer growth.The XRD results show that the pure Conanotubes have polycrystalline hexagonal close packed(HCP)crystal structure with(110)preferred orientation,but the Co-Dy alloy nanotubes are mostly amorphous.For the Co-Cu multilayer nanotubes/nanowires,the diffraction peak of Co(002)and Cu(111)can be observed simultaneously in the XRD patterns.The study of the magnetic properties of the samples measured by vibrating sample magnetometer(VSM)found that the dope of Dy element could improve the coercivity of the Co nanotube arrays,and the annealing treatment could improve the magnetic anisotropy of the samples.For Co-Dy alloy nanotubes,the easy magnetization direction was always along the axis of the nanotubes.For Co-Cu multilayer nanotubes/nanowires,as the thickness of the non-ferromagnetic Cu layers increases,the out-of-plane coercivity of the samples gradually decreases.While the in-plane coercivity of the samples has been less influenced,because of the interaction between the ferromagnetic Co layer decreases.In this paper,the Object Oriented Micro Magnetic Framework(OOMMF)was used to study the magnetic reversal process and mechanism of Co nanotube.The simulation results show that the coercivity of Co nanotube increases with the increase of aspect ratio.When the value of external magnetic field reaches the switch field,the magnetization reversal center first forms at both ends of the nanotube and drives the magnetic moment surrounding to reverse,then magnetization of the whole nanotube is reversed as the center gradually propagates to the middle.