Preparation And Study Of The Co/Cu Multilayer Nanowires

One dimensional magnetic nanomaterials have gained wide attention from scientificresearches in the last decades due to their unique physical properties and potential applications in the magnetic recording,nanosensorsand spintronics,etc.In the mean time,a large number of preparation methods have been explored and developed to prepare one dimensional magnetic nanomaterials,among those preparation methods,the most widely-used preparation method of the high-aspect-ratio nanowires is template-assisted electrochemical deposition technique because of its convenience,simplicity and low-cost compared to many other praparation methods that have been applied,for example,magnetron sputtering,chemical vapor deposition and molecular beam epitaxy,etc.So it has become a hot topic about its preparation techniques and how to improve its giant magnetoresistance properties.Therefore the paper is presented as follows:(1)Highly ordered and homogeneously aligned PAA templates were prepared by the two-step anodization in 0.3 M oxalic acid.A series of nanowires arrays were fabricated by single-bath electrodeposition method,including Co nanowires,Cu nanowires and Co/Cu multilayered nanowires.The morphology and structure were measured by scanning electron microscopy(SEM)and transmission electron microscopy(TEM)and the magnetic properties were characterized by vibrating sample magnetometer(VSM),the giant magnetoresistance properties were measured by physical property measurements(PPMS).It is found that the nanowires were highly ordered with a diameter of 50 nm,the filling density is very high and the structure is polycrystalline,the nanowires have obvious magnetic anisotropy and the easy magnetization axis is parallel to the long axis of the nanowires.At the same time,the influence of the solution concentration and deposition voltage on the morphology,structure and magnetic properties were also studied,it is found that the morphology,structure and magnetic properties of the nanowire arrays were affected by the concentration change of the solution during the deposition process and the change of deposition voltage.(2)A series of samples with different number of cycles,thickness of magnetic layer,nonmagnetic layer thickness of different nanowire arrays were prepared by changing the experimental conditions respectively,and at the same time,we study the influence of thesefactors on the magnetic properties of the multilayered nanowire arrays and GMR effect,besides we also analyze the specific reasons.We made some improvements about the structure of the nanowires in order to make it better applied to the practical field.It is found that the coercivity(Hc)and remanence ratio(Mr/Ms)increase with the increase of the nonmagnetic layer thickness and period number of multilayered nanowires,the GMR value showed a phenomenon of oscillation with the increase of the nonmagnetic layer thickness,and decreases with the increase of cycle number.The coercivity(Hc)and remanence ratio(Mr/Ms)increase with the increase of the magnetic layer thickness and the GMR value increases first and then tend to decrease.Which of all above are attributed to the spin dependence scattering.