Magnetic and structural properties of Fe–Co nanowires fabricated by matrix synthesis in the pores of track membranes

Fe$_{1-x}$Co$_x$ nanowires are obtained by electrochemical deposition into the pores of track-etched membranes. The characteristics of the growth process that allow controlling the length and aspect ratio of the nanowires are established. The elemental composition and magnetic properties of the nanowires depend on the diameter of the track-etched pores, which varies from $30$ to $200$ nm, and the electrochemical potential $U$ ($650$–$850$ mV), which determines the nanowire growth rate. According to the results of elemental analysis and the Mössbauer spectroscopy data, the Co content in Fe$_{1-x}$Co$_x$ lies in the range of $x=0.20$–$0.25$. It is found that the orientation of the magnetic moment of Fe–Co nanoparticles in the wires depends both on the track pore size d and on the nanowire growth rate. Thus, the magnetic moments in nanowires grown in $50$-nm-diameter pores are oriented within $0^\circ$–$40^\circ$ with respect to the nanowire axis. The magnetic properties of the nanowires are explained in the framework of a theoretical model describing the magnetic dynamics of nanocomposites, which was extended to include the relaxation of the magnetization vector and to take into account interaction between the particles. The key physical parameters important for the technological applications of the nanowires are determined, their dependence on the nanowire growth conditions is traced, and the possibility of controlling them is established.