Comparison of two measurement methods for Curie temperature and related theoretical calculation
The Curie temperature Tc,a ferromagnetic physical parameter,was investigated theo-retically and experimentally by taking 63 nm(average diameter)spherical Ni particles as an example.Based on the cohesive energy model and the theory of metal vibration entropy,the relationship be-tween Curie temperature and particle size of spherical ferromagnetic nanoparticles was deduced from the two theoretical methods,and then the theoretical Tc values were calculated to be 350.3 ℃ and 351.0 ℃,respectively.TG/DTA curve and thermomagnetic curve(namely the magnetization M va-ries with the temperature T)were measured by thermogravimetric/differential thermal analyzer(TG/DTA)and vibrating sample magnetometer(VSM),respectively.The phase transition peak of DTA curve gave Tc value of 353.0℃,and the linear extrapolation ofM-1-T curve gave Tc value of 350.0 ℃.The error between the two experimental values,as well as between all theoretical values and experimental values,was less than 3.0 ℃.This indicated that the model had strong applicability for the current study,and thus the TG/DTA method for measuring Tc was reliable.
Curie temperaturesize dependencemagnetic phase transitionCurie-Weiss lawco-hesive energy
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