K. Maaz

Effect of aging on the magnetic characteristics of nickel nanowires embedded in polycarbonate

Single crystalline Ni nanowires (with a controlled diameter of ∼14 nm) have been fabricated by electrochemical deposition in etched ion-track polycarbonate templates. The exchange bias effect in these nanowires has been studied at 10 K under a cooling field of 10 kOe applied parallel to the wire axis for different time intervals starting from the as-fabricated to ∼2 yr old samples. A continuous drop in the saturation magnetization has been observed with time due the formation of an antiferromagnetic oxide layer at the periphery of nanowires. A model for the drop of magnetization has been used to calculate the thickness of the oxide layer in nickel nanowires. The observed variation in exchange bias and saturation magnetization has been explained by taking into account the exchange interactions at the Ni-NiO interface and the development of antiferromagnetic NiO at the expense of metallic Ni.

Fabrication and Magnetoresistance of Single Au-Ni-AuNanowire

Magnetoresistance of Au-Ni-Aunanowire with 300 nm long nickel segment sandwiched between the gold segmentsis studied. Struc- tural analysis of the sample is performed by X-ray diffraction and transmission electron microscopy, which reveals the pure phase, crystalline behavior of the nanowires. Magnetic measurements of the samples confirm ferromagnetic behavior due to the presence of nickel in the wires. Current versus voltage measurement of single nanowire bridged between the two gold electrodes shows ohmic behavior at room temperature with a resistance of 73 Ω. Magnetoresistance as a function of the applied field shows a decreasing trend of resistance below 140 Oe, followed by an increasing trend in resistance in the field range 140 Oe 250 Oe. The results have been explained with reference to the variation of magneto-resistance upon the alignment of spins, formation of magnetic domains and their propagation along the direction of magnetic field.