Evidence of phase separation in magnetic colloids using magnetic resonance

Magnetic resonance of a surfacted magnetite-based magnetic fluid was investigated in a temperature range from 100 to 300 K. The magnetic resonance spectra were discussed in terms of contributions due to magnetic centers from isolated nanoparticles and dimers. The magnetic resonance data showed two distinct transitions. One due to a solid-liquid transition around 180 K for the colloid liquid carrier, whereas the second one near 240 K was attributed to phase separation. The spectra area analysis strongly supports our conclusions and additionally suggests the formation of agglomerates prior to the phase separation.