Magnetic properties of ε ‐Fe 3–x Ni x N nanoparticles

Abstract

The pseudo-binary ε-Fe3–xNixN system with x = 0.0 to 0.3 in the nanosize range (20–25 nm) is studied for magnetic interactions among the particles. The decomposition of citrate precursors in air and nitridation in NH3 gas gives the desired compositions. For all the compositions, the X-ray diffraction patterns are indexed based on the ε-Fe3N hexagonal phase with the space group P63/mmc. The magnetization vs. field curves do not saturate even at higher applied fields, showing super-paramagnetic nature, which is confirmed from 57Fe Mössbauer spectroscopy experiments. The room temperature saturation magnetization (σs) and Curie temperature (Tc) increase with the increase of Ni concentration from x = 0.1 to 0.3. However, the σs values at 5 K decrease steadily but slightly with the increase of Ni content from x = 0.1 to 0.3. The zero-field cooled (ZFC) and field cooled (FC) measurements are recorded from room temperature down to 10 K, with an applied field of 0.025 Tesla and these curves bifurcate at a higher temperature below 300 K because of large inter-particle interactions. The blocking temperature (TB) is measured from the magnetic measurements and is found to increase from 20.35 K to 28.14 K for x = 0.1 to 0.3 compositions respectively. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)