CTAB-mediated synthesis of iron–nickel alloy nanochains and their magnetic properties

One-dimensional nanochains consisting of crystalline iron–nickel nanoparticles were successfully synthesized by a simple cetyltrimethylammonium bromide (CTAB) mediated assembly method. The structure and magnetic properties of the nanochains were investigated. The product is composed of nanochains with a diameter of about 90–110 nm and length about several micrometers. A possible formation mechanism of these 1D particle assemblies was proposed. It was found that CTAB can serve as an effective cross-linker and plays an important role in the formation of nanochains. CTAB with low concentration can adsorb on the surface of particles and partially compensate the negative surface charge, leading to an anisotropic distribution of the residual surface charges. And this extrinsic electric dipole formation is responsible for the linear organization of the particles into chains. As-prepared iron–nickel nanochains exhibit ferromagnetism at room temperature with a much enhanced magnetic coercivity over three orders of magnitude larger than that of bulk permalloy. The imaginary part μ″ of the permeability for FeNi3-chain/wax composite shows a broad resonance peak in the frequency range 150 MHz to 4 GHz. Meanwhile, the position and width of resonance peak can be tuned via magnetic-field orientation treatment.