Complex magnetic interactions and charge transfer effects in highly ordered NixFe1−x nano-wires

Abstract

This work investigates the subtle magnetic interactions within the NixFe1−x (x=0.3, 0.5, and 1.0) nano-wires by probing spin-dependent behaviors of the two constituted elements. The wires were fabricated by electro-deposition and an anode aluminum oxide template to produce free-standing nature, and the Ni–Fe interactions were probed by x-ray magnetic spectroscopy across a BCC→FCC structural transition. The wires' magneto-structural properties were predominated by Ni, as reflected by a decrease but an increase in total magnetization and FCC x-ray intensity with increasing x, even if the Fe moment increased simultaneously. Upon annealing, a prominent charge transfer, together with the changes of spin-dependent states, took place in the Ni and Fe 3d orbitals, and a structural disordering was also obtained, for the wires at x=0.3. The charge transfer led to a local magnetic-compensation for the two elements, explaining the minor change in total magnetization for x=0.3 probed by a vibrational sample magnetometer. When x was increased to 0.5, however, the charge transfer became inactive due to persistent structural stability supported by Ni, albeit resulting in nearly invariant magnetization similar to that of x=0.3. The complexity of the Ni–Fe interactions varied with the composition and involved the modifications of the coupled magnetic, electronic and structural degrees of freedom. The study identifies the roles of Ni and Fe as unequally-influential in NixFe1−x, which provides opportunities to re-investigate the compound's properties concerning its technological applications.