Perpendicular Giant Magnetoresistance and Magnetic Properties of Co/Cu Nanowire Arrays Affected by Period Number and Copper Layer Thickness

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.

Modulated critical currents of spin-transfer torque-induced resistance changes in NiCu/Cu multilayered nanowires

“…Intermediate configurations of magnetic layers except for the fully antiparallel (AP) and fully parallel (P) configurations can exist; therefore, more than one free layer might contribute to the MR and STT effects discussed below. They can be understood by the unequal coercivities and interaction of different NiCu layers due to the varying thickness of the NiCu and Cu layers [ 10 , 21 ].…”

“…In most reported works, the nanowires were deposited in all pores of the AAO templates [18][19][20][21]. Additional etching steps or coating steps were necessary to define the contact area and to obtain a small contact array, which complicates the fabrication process [18,19].…”

Determination of Cobalt Spin-Diffusion Length in Co/Cu Multilayered Heterojunction Nanocylinders Based on Valet–Fert Model

“…Piraux et al and Blondel et al demonstrated the current perpendicular-to-plane giant magnetoresistance (CPP-GMR) effect by using the Co/Cu multilayered nanocylinders which were electrodeposited into ion-track-etched polycarbonate membranes [ 8 , 9 ]. After that, several research works have been reported that the CPP-GMR effect was observed in the ferromagnetic multilayered nanocylinders which were electrodeposited into anodized aluminum oxide (AAO) templates [ 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 ]. Evans et al reported that the Co-Ni/Cu multilayered nanocylinders, which were electrodeposited into commercially available AAO membranes (~300 nm in diameter, D and ~60 µm in length, L ), exhibited a CPP-GMR effect of ~55% at room temperature [ 10 ].…”

“…Zhang et al also reported that Ni-Fe/Cu/Co/Cu multilayered nanocylinders, which were electrodeposited into home-made AAO templates ( D = 120 nm), exhibited a GMR effect of ~45% at room temperature [ 15 ]. Han et al reported that the Co/Cu multilayered nanocylinders in home-made AAO templates ( D = 50 nm) showed a CPP-GMR effect of ~13% at room temperature [ 16 ]. They revealed that t Co of ~50 nm and t Cu of ~5 nm were optimum values to demonstrate a large CPP-GMR effect.…”