基于伊辛模型的Fe_(0.5)Mn_(0.1)Al_(0.4)合金磁化强度和磁熵变蒙特卡洛模拟

基于伊辛模型的单自旋反转蒙特卡洛算法,考虑了粒子间的最近邻以及次近邻相互作用,研究了无序Fe0.5Mn0.1Al0.4合金的磁化强度和磁熵变.首先,强调了粒子间的次近邻相关作用对体系的磁性和热力学性质的影响,明确了次近邻相互作用系数,证实了低温合金阻挫的存在;其次,研究了在相变温度处(不同磁场下)磁化强度随外加磁场(温度)的变化情况以及磁性粒子对磁化强度的贡献,发现反铁磁性粒子Mn在低温区对Fe0.5Mn0.1Al0.4合金的相变起了主要作用,而高温区体系的相变是由铁磁性粒子Fe贡献的;最后,分析了体系在相变温度处磁熵变数值随外加磁场的变化情况以及磁熵变在不同的外磁场下随温度的变化情况,当外加磁场H=0.14(a.u.)时,Mn粒子在冻结温度处的平均磁化强度为零,体系处于最无序的状态,对应的磁熵变ΔS(0.1,0.14)达到了正向最大值,极值的位置对应于体系的相变温度.

The magnetization and magnetic entropy change of Fe0.5Mn0.1Al0.4 alloy by means of Monte Carlo simulation on the basis of Ising model

By means of single spin flip Metropolis dynamics on the basis of a random site-diluted three-dimensional Ising model with nearest-neighbor interactions and next-nearest-neighbor interactions, the magnetization and magnetic entropy change of alloy are researched. Firstly, the influence of next-nearest-neighbor interactions on magnetic and thermodynamic properties of the system is emphasized, from which next-nearest-neighbor interaction coefficient is determined, and the existence of frustration in the low temperature is also confirmed. Secondly, In the phase transition temperature magnetization as a function of magnetic field or under different magnetic field magnetization as a function of temperature and contribution of magnetic particles to the magnetization are studied, we conclusively demonstrate that the antiferromagnetic Mn particle plays a crucial role in determining low-temperature phase transition, whereas the high-temperature phase transition is contributed mainly by Fe component. Finally, external magnetic field dependence of magnetic entropy change is analyzed on the phase transition temperature, the magnetization of the antiferromagnetic Mn particle is zero on freezing temperature when external magnetic field is 0.14, which show the system is the most disorder condition and the corresponding magnetic entropy change reached a positive maximum value . Furthermore, from magnetic entropy change as a function of temperature curve under different magnetic field can determine phase transition temperature of the system.