Temperature dependence of FMR spectrum of Fe3C magnetic agglomerates

Abstract

The sample of iron carbide has been prepared using carburisation of iron with ethylene/hydrogen mixture. After carburisation, the sample was characterized by using XRD and scanning electron microscopy. XRD revealed the presence of cementite phase only. The mean size of cementite crystallites was determined to be 46 nm. The FMR absorption signals have been investigated in the temperature range from liquid helium up to room temperature. The asymmetric, very broad and intense FMR line was registered and decomposed in two Lorentzian-shape components (low- and high-field). The main high-field component shifts toward low magnetic fields with decreasing temperature. At 75 K a phase transition was observed due to the freezing of the non-magnetic matrix. Additionally, the spin glass state was recorded below 30 K. © 2005 IOP Publishing Ltd.