Effect of magnetic fields on solid-melt phase transformation in pure bismuth

The differential thermal analysis (DTA) apparatus has been designed in order to investigate the effect of magnetic fields on solid-melt phase transformation in pure bismuth. The endothermic peaks of DTA curves show that melting is insensitive to magnetic fields, which can be verified from thermodynamics. However, the exothermic peak obviously shifts to higher temperature as the magnetic field strength increases, from which the magnetic field does not affect the crystal growth but nucleation. On the basis of the assumption that there is an intermediate state between a crystal nucleus and a liquid atom, one possible reason for the shift of exothermic peaks is that kinetic barrier of nucleation is lowered and nucleation is activated by magnetic fields.