Optimization of growth conditions to obtain highly anisotropic FeCo nanowires prepared through magnetic-field-assisted chemical route

Abstract

In this study, we synthesized one-dimensional α-FeCo nanowires using the magnetic-field-assisted hydrazine reduction method. The amount of hydrazine, NaOH, synthesis temperature and strength of the magnetic field were optimized to obtain high aspect ratio nanowires with good quality. Two samples, obtained at 90 °C (S12) and 60 °C (S34) with improved morphologies and aspect ratios, while keeping the other optimized conditions (Hydrazine - 1 mL; NaOH - 1.5 g and strength of the magnetic field - 4000 Gauss (G)) same, were characterized using various techniques viz. X-ray diffraction (XRD), High-resolution transmission electron microscopy (HR-TEM), selected area electron diffraction (SAED), X-ray photoemission spectroscopy (XPS) and dc-magnetization to investigate structural, electronic structural and magnetic properties. Both the samples revealed single-phase α-FeCo formation with body centered cubic (BCC) geometry with space group: Im-3m indicating decrease in the lattice parameter and crystallite dimensions at 60 °C (S34). The influence of synthesis temperature was notably observed on the magnetic properties as well. The saturation magnetization was found to be enhanced from 233 emu/g for S12 to 247 emu/g for S34 along with the enhancement in coercivity. The effective magnetic anisotropy also enhanced to be 2.3× 106 erg/cm3 in S34. In brief, the improvement in aspect ratio and morphology of the wires resulted in the enhancement of saturation magnetization and effective magnetic anisotropy. The enhanced value of magnetocrystalline anisotropy and shape magnetic anisotropy is attributable to the external magnetic field applied during growth and curling of spins due to the reduced diameter of the wires.