Electronic and magnetic structure of Fe/Co-doped multiwalled carbon nanotubes using X-ray absorption and magnetic circular dichroism spectroscopy

Abstract

Multi-walled carbon nanotubes (MWCNTs), synthesized using the microwave plasma-enhanced chemical vapor deposition (MPCVD) technique, have been examined to elucidate their electronic and magnetic structures through near-edge X-ray absorption fine structure (NEXAFS) and X-ray magnetic circular dichroism (XMCD) spectroscopy. NEXAFS analysis at the Fe and Co L-edges reveals the presence of Fe-metal nanoparticles embedded within the CNT lattice, along with divalent Co ions coordinated to the matrix in an octahedral symmetry. Furthermore, the appearance of two distinct NEXAFS peaks between the pi* and sigma* transitions indicates 1s to sp(3) hybridization, attributed to the interaction of Fe and Co2+ ions with the carbon nanotube structure. Additionally, XMCD spectra confirm that MWCNTs exhibit room temperature ferromagnetism, primarily driven by Fe-C and Co-C bonding within the nanotubes. This intrinsic ferromagnetic behavior, along with the high aspect ratio and unique electronic properties of MWCNTs, highlights their promising potential for applications in spintronic storage devices.