Direct synthesis of L10 FePt nanoparticles within carbon nanotubes by wet chemical procedure

This paper reports on the low temperature synthesis of L10 iron–platinum (FePt) particles within multiwall carbon nanotubes using a novel wet chemical method that allows the filling of the nanotube cavity keeping clean its external wall. In the proposed procedure, nanotubes are filled with a precursor salt of hexaaquairon(II) hexachloroplatinate, ([Fe(H2O)6][PtCl6]) and nanoparticles of the magnetically hard phase are directly obtained by heating at 400 °C in a reductive atmosphere. The advantage of such a precursor, allowing one to obtain at low temperature the L10 phase without passing through the soft fcc phase, is due to its structure, where the Fe and Pt atoms are arranged in alternating planes, as in the fct FePt structure. Morphological, structural and magnetic properties of the filled nanotubes have been investigated by transmission electron microscopy, x-ray diffraction and magnetization measurements. The results show the coexistence of nanoparticles in the superparamagnetic and blocked state, depending on the temperature, due to the particle size distribution.