THE DETERMINATION OF CURIE-TEMPERATURE BY DIFFERENTIAL SCANNING CALORIMETRY UNDER MAGNETIC-FIELD

Many different methods to measure magnetic Curie temperature (Tc) have been developed in the past. Differential scanning calorimetry (DSC) is a convenient and accurate method for measuring Tc in terms of the observation that the heat flow has a visible variation at the transition point. Some ferromagnetic materials such as Metglas* 2714A shows a weak response to the Curie transition on DSC curve, others, e.g., amorphous (Fe0.9Nb0.1)80B20 (nominal composition), show even less change on the curve, which makes the detection of Tc very difficult. An improved method presented in this paper is to apply an axial magnetic field on samples during the DSC scanning process. The heat flow change of the samples at the Curie transition is amplified and a sharp : Tc is easily observed. The dc or ac magnetic field applied during the DSC scan was generated by a solenoid surrounding the DSC cell. The improved DSC results show that dc field is more effective in amplifying the transition phenomenon than ac field. The value of Tc is not altered significantly under low-applied-field ( from 0 to 5600 Amperes/meter). The procedure can improve the ability of DSC when measuring magnetic Curie transition. The results are acceptable when compared to other methods.