Magnetic properties of nanocrystalline ɛ-Fe3N and Co4N phases synthesized by newer precursor route

Nanocrystalline ɛ-Fe3N and Co4N nitride phases are synthesized first time by using tris(1,2-diaminoethane)iron(II) chloride and tris(1,2-diaminoethane)cobalt(III) chloride precursors, respectively. To prepare ɛ-Fe3N and Co4N nitride phases, the synthesized precursors were mixed with urea in 1:12 ratio and heat treated at various temperatures in the range of 450–900 °C under the ultrapure nitrogen gas atmosphere. The precursors are confirmed by FT-IR study. The ɛ-Fe3N phase crystallizes in hexagonal structure with unit cell parameters, a = 4.76 Å and c = 4.41 Å. The Co4N phase crystallizes in face centred cubic (fcc) structure with unit cell parameters, a = 3.55 Å. The estimated crystallite size for ɛ-Fe3N and Co4N phases are 29 nm and 22 nm, respectively. The scanning electron microscopy (SEM) studies confirm the nanocrystalline nature of the materials. The values of saturation magnetization for ɛ-Fe3N and Co4N phases are found to be 28.1 emu/g and 123.6 emu/g, respectively. The reduction of magnetic moments in ultrafine materials compared to bulk materials have been explained by spin pairing effect, lattice expansion, superparamagnetic behaviour and canted spin structures at the surface of the particles.