Calorimetric study of magnetic fluids under a magnetic field

In our past study, it was found that the strong magneto-optical effect of a magnetic fluid (MF) under a magnetic field is due to the second-order phase transition from colloidal particles' monodispersed phase to the particles' anisotropically agglomerated microclusters phase. These results, however, contradicted the Landau criterion. In the present study, in order to clarify whether the transition is of first order or second order, we performed differential scanning calorimetry (DSC) experiments on three different MFs to look for the existence of a phase transition latent heat. The DSC measurement was performed in the temperature range 22-150 degrees C with zero magnetic field and under approximately 10 kA/m magnetic field, respectively. No phase transition heat was observed within an experimental error of 0.03 kJ/kg for all the samples whether or not the field was applied.