Effect of aspect ratio and temperature on magnetic properties of permalloy nanowires.

Abstract

Arrays of permalloy nanowires (NWs) were fabricated into the pores of self-engineered Anodic Aluminium Oxide (AAO) templates by a simple electrodeposition technique (EDT) with a diameter -200 nm. By varying the length of the nanowires from 1.5 to 7.5 microm, got corresponding changes in aspect ratio from 7.5 to 37.5. We studied the growth and structural properties of permalloy nanowires using scanning electron microscopy, X-ray diffraction spectra and transmission electron microscopy. We performed the magnetic measurements of permalloy nanowires using vibrating sample magnetometer. The coercivity (H(c)) and anisotropy field (H(an)) observed considerably higher when the applied magnetic field was perpendicular to the nanowires axial direction (In-Plane) compare to the applied magnetic field was parallel to the nanowire axial direction (Out-of-plane). Reverse trend was observed for the maximum remanent ratio (M(r)/M(s)). So we concluded that the magnetic easy axis of the permalloy nanowires are along the axial direction of the nanowires and magnetic hardness of the nanowires higher in transverse direction compare to the axial direction of nanowires. For the first time temperature (80 K < or = T < or = 300 K) and aspect ratio dependence magnetic properties of the permalloy nanowires have been studied in detail.