具有铁磁性Ising模型的磁性质

The Magnetic Properties of Ferromagnetic Ising Model

以Fe4N为原型,构建在晶场作用下的混自旋Ising模型。利用平均场理论,得到该模型的磁矩和自由能公式;绘制了不同相互作用下的磁化曲线;研究了系统的磁性质。发现系统发生了丰富的相变特性:系统存在一级有序-无序相变、重入现象和二级相变;晶场D_A/|J_1|和D_B/|J_1|对系统的磁性质所起作用相似。随着晶场的增加,一级有序-无序相变的温度升高,重入现象的温度降低;一级有序-无序相变和重入现象的温度间距逐渐缩小,直至这两种相变消失。

Using the mean field theory,the mixed spin Ising model with crystal field based on Fe4N structure was studied.The expressions of magnetization and free energy were obtained,the magnetization curves were plotted with different exchange interactions,and the magnetic properties of the system were researched.It was found that there were abundant phase transition characters in the system.first order—disorder phase transitions,reentrant phenomenon and second order phase transitions.The effects of crystal field DA/｜J1｜ and DB/｜J1｜on the magnetic properties of the system were similar.With the increase of crystal field the temperature of first order—disorder phase transition was getting higher,the temperature of reentrant phenomenon was getting lower.The temperature interval of first order—disorder phase transition and reentrant phenomenon was narrowing,until these two kinds phase transitions vanished.