Amorphous FexCo1–x wire-like nanostructures manufactured through surfactant-free magnetic-field-induced synthesis

Marcin Krajewski , Sz-Chian Liou , Wen-An Chiou , Mateusz Tokarczyk , Artur Małolepszy , Magdalena Płocińska , Agnieszka Witecka , Sabina Lewińska , Anna Ślawska-Waniewska

Abstract

So far, it has been proven that the magnetic-field-induced (MFI) synthesis is a process which mainly leads to the formation of magnetic metallic one-dimensional nanostructures. Taking advantage of this method, the new procedures which allow manufacture of the magnetic bimetallic iron–cobalt wire-like nanochains with Fe0.75Co0.25, Fe0.50Co0.50, and Fe0.25Co0.75 compositions are demonstrated in this work. They were produced through a simple one-step magnetic-field-induced (MFI) chemical co-reduction of three different mixtures containing a proper amount of Fe2+ and Co2+ ions with aqueous sodium borohydride solution as the reducing agent. The synthesis process was carried out at room temperature without the use of templates, surfactants, complexing agents, and organic solvents. The morphological and structural studies indicated that all as-prepared materials were amorphous, and they were composed of nanoparticles aligned in almost straight chains. Moreover, they revealed the core–shell structures with bimetallic alloy cores containing desired iron-to-cobalt ratios and very thin oxide shells. Furthermore, the obtained nanostructures behaved as ferromagnetic materials. Their magnetic properties were correlated with their structural properties and chemical compositions. It was observed that their saturation magnetization decreased significantly with increasing content of cobalt in the chains, whereas the variation of their coercivity was less pronounced.