Fabrication And Magnetic Property Of Cu/Ni Multilayered Nanowires

The discovery of giant magnetoresistance (GMR) in metallic multilayers has led to numerous developments in both fundamental and applied fileds. Such structures are composed of thin alternating magnetic and nonmagnetic layers. Due to interactions between the electron spin and the magnetisation of consecutive magnetic layers, their electrical resistance is highly sensitive to an external magnetic filed.Anodic aluminum oxide (AAO) template has been prepared by a two-step anodization process in this paper, and the aperture of the AAO template could be changed according to demands by adjusting the technologic parameters of anodization and electrodeposition. The ordered multilayered Cu/Ni nanowires arrays have been prepared by electrodeposition into the pores of the anodic aluminum oxide (AAO) template in dual bath. Scanning electronic microscopy (SEM), transmission electron microscopy (TEM) was used to characterize the morphology of Cu/Ni multilayered nanowires arrays. Vibrating sample magnetometer (VSM) was used to test the magnetic characterization of the Cu/Ni multilayered nanowires arrays. The GMR ratios of the samples were measured by four-probe measurement.SEM images reveal that the surface of the nanowire is smooth and uniform,which corresponds to the pore size of the used AAO template. Selected-area electron diffraction (SAED) result demonstrates that those multiplayered nanowires exhibit single crystal structures. The feature of Ni segments alternated with Cu layers is clearly seen in the TEM images, and the layer thickness of the nanowires could be changed according to demands by adjusting the quantity of electrodeposition. The result of hysteresis loops shows that Cu/Ni nanowires arrays have a strong perpendicular magnetic field anisotropy. When the magnetic field is perpendicular to the AAO template, the squareness (0.2951, 0.5167, 0.7435, 0.6661) are much enhanced compared to that of parallel to the AAO template (0.06824, 0.04735, 0.01965, 0.09133).Besides, the modulated thickness and the diameter of nanowires on the magnetic characterization of the Cu/Ni multilayered nanowires have been studied in this paper. The coercivity of Cu/Ni multilayered nanowires is enhanced with the increase of modulated thickness and the decrease of the diameter of the Cu/Ni multilayered nanowires. The GMR value close to 25.6% were obtained at 300K for a 60μm long Cu(8nm)/Ni(40nm) multilayered nanowires with 80-nm diameter embedded in the membrane.