XRD, TEM and magnetic resonance studies of iron carbide nanoparticle agglomerates in a carbon matrix Original Research Article

Three powder samples with different content of iron carbide in a carbon matrix have been synthesised by carburisation of nanocrystalline iron with methane. The samples have been characterised by XRD and TEM methods. The mean crystallite size of the obtained iron carbide has been found to be in the range from 41 to 67 nm. The magnetic resonance measurements of these samples have been performed at room temperature. Very intense magnetic resonance lines have been recorded for each of the samples. A resonance field, an integral intensity and a linewidth strongly depend on the concentration of iron carbide. The observed magnetic resonance lines have been fitted with two Lorentzian-shape lines, one centred at lower and the other at higher magnetic fields. Strong magnetic anisotropy was observed for all the samples and for the sample with lower concentration of iron carbide it is more intense. The resonance absorption signal arises from the agglomerates of iron carbide nanoparticles interacting strongly among themselves. The observed shift of the resonance field is connected with a strong ferromagnetic interaction between agglomerates of nanoparticles.