Abstract
One-dimensional magnetic nanowires have attracted much attention in the last decades due to their unique physical properties and potential applications in magnetic recording and spintronics. In this work, ordered arrays of Co/Cu multilayered nanowires which can be exploited to develop magnetoresistive sensors were successfully prepared using porous anodic alumina (PAA) templates. The structure and morphology of the multilayered nanowire arrays were characterized by transmission electron microscopy and scanning electron microscopy. The nanowire arrays are highly ordered and the average diameter is about 50 nm, which is controlled by the pore diameter of the PAA templates. The influences of period number and Cu layer thickness on the magnetic and the giant magnetoresistance (GMR) properties were investigated. The coercivity and remanence ratio increase first and then gradually tend to be stable with the increase of period number and the Cu layer thickness, while the GMR ratio increases first and then decreases with the increase of the period number accompanied by an oscillatory behavior of GMR as the Cu layer thickness changes, which are ascribed to the spin dependence electron scattering in the multilayers. The optimum GMR of −13% appears at Co (50 nm)/Cu (5 nm) with 200 deposition cycles in our experimental conditions.
Highlights
Giant magnetoresistance (GMR) effect is a phenomenon where the resistivity of the material will be affected significantly with the application of an external magnetic field
Multilayered nanowires consisting of alternating magnetic and nonmagnetic layers are an ideal system to investigate GMR effect in the current perpendicular to the plane (CPP) geometry as it has been shown to exhibit a more significant GMR effect and high aspect ratio of the multilayered nanowires leading to larger resistance that enables high accuracy in the measurements [4]
Great efforts have been devoted to the research on the CPP-GMR of CoNi/Cu [9,10,11], NiFe/Cu [12,13,14], and Co/Cu [7, 15,16,17] multilayered nanowires and it has been shown that the GMR and the magnetic properties of multilayer nanowire arrays are affected by a variety of factors, including the structure of the materials, wire diameter, wire total length, composition, layer thickness, and other factors
Summary
Giant magnetoresistance (GMR) effect is a phenomenon where the resistivity of the material will be affected significantly with the application of an external magnetic field. Great efforts have been devoted to the research on the CPP-GMR of CoNi/Cu [9,10,11], NiFe/Cu [12,13,14], and Co/Cu [7, 15,16,17] multilayered nanowires and it has been shown that the GMR and the magnetic properties of multilayer nanowire arrays are affected by a variety of factors, including the structure of the materials, wire diameter, wire total length, composition, layer thickness, and other factors. Co/Cu multilayered nanowire arrays were prepared in PAA templates via single bath by electrochemical method and the effects of repeat period number and copper layer thickness on magnetic properties and CPP-GMR of Co/Cu nanowire arrays were studied. It is evident from the experiment that the periodicity of the multilayered nanowires and the nonmagnetic layer thickness play a crucial role in deciding the magnetic and CPP-GMR of the multilayered nanowire arrays
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