Growth and characterization of highly textured γ'''- iron nitride nanoparticles

Full text: Iron nitrides are important industrial materials because of its mechanical and magnetic properties. Iron nitride films and particles have been prepared by various methods [1-2]. The Fe-N system shows a very complex phase diagram where iron nitrides can exist in many different phases. FeN has been reported to have two phases: γ''-FeN (ZnS structure) and γ'''-FeN (NaCl) structure. These two phases are generally formed simultaneously, making it difficult to produce a single phase [2, 6]. Studies report that the phases γ''-FeN and γ'''-FeN are paramagnetic and antiferromagnetic at low temperatures, respectively[3]. In this work single-phase γ'''-FeN nanoparticles with the rock-salt structure was produced by pulsed laser deposition of Fe onto a Si(100) substrate in 1 Torr pressure N₂ atmosphere. For the ablation a Nd:YAG excimer laser (λ=1064 nm) was used, operating at a repetition rate of 10 Hz and 0.3 J per pulse, with 7 ns pulse width. The obtained nanoparticles were characterized by X-ray diffraction (XRD) showing a single γ'''-FeN phase. X-ray photoelectron spectroscopy (XPS) spectra exhibits six Fe 2p peaks including two 2p_3/2 peaks, two 2p_1/2 peaks, and their two satellite peaks.The magnetic properties of this sample were studied by a vibrating sample magnetometer (VSM). The obtained hysteresis loops at 5 K and the magnetization vs. temperature curves (field cooling and zero field cooling) showed a clear antiferromagnetic behavior. References: [1] Prieto P., Macro, J.F., Sanz, J.M.: Surf. Interface Anal.40, 781 (2008). [2] Jirásková Y., Hvlícek S., Shneeweiss O.,Perina V., Blawert C.:J. Magn. Magn. Mater.234,477(2001) [3] Usui, R., Yamada, Y., Kobayashi, Y.: Hyperfine Interact.205, 13 (2012). (author)