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
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摘要
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.
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 Fe0. 5Mn0. 1Al0. 4alloy 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,the 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 a. u.,which shows the system is the most disorder condition and the corresponding magnetic entropy change ΔS( 0. 1,0. 14) reaches a positive maximum value. Furthermore,from magnetic entropy change as a function of temperature curve under different magnetic fields,onecan determine the phase transition temperature of system.
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 Fe0. 5Mn0. 1Al0. 4alloy 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,the 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 a. u.,which shows the system is the most disorder condition and the corresponding magnetic entropy change ΔS( 0. 1,0. 14) reaches a positive maximum value. Furthermore,from magnetic entropy change as a function of temperature curve under different magnetic fields,onecan determine the phase transition temperature of system.
引文
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[2]Tarigan K.Local ordering study of nanostructure Fe Mn Al alloys[J].IEEE Trans.Magn.,2009,45(6):2492.
[3]Pea Lara D,Diosa J E,Lozano C A.Blume-Capel spin-glass model for Fe-Mn-Al alloys[J].Phys.Rev.E,2013,87(3):032108.
[4]Restrepo J,Pérez Alcázar G A.Magnetic properties of disordered Fe0.9-xMn0.1Alxalloys[J].J.Appl.Phys.,2000,87(10):7425.
[5]Mohan T V S M,Bansal C.Mssbauer effect in atomic ordered and disordered Fe0.75-xMnxAl0.25alloys[J].Phys.Stat.Sol.(b),1996,193:167.
[6]Pérez Alcázar G A,Plascak J A,Galvo da Silva E.Magnetic properties of Fe-Mn-Al alloys in the disordered phase[J].Phys.Rev.B,1988,38:2816.
[7]Restrepo J,Pérez Alcázar G A.Interpretation based on a binomial method of the hyperfine field distributions of disordered:Fe0.9-xMn0.1Alxalloys[J].J.Magn.Magn.Mater.,2000,213(1):135.
[8]Rosales Rivera A,Pérez Alcázar G A,Plascak J A.Diluted and random-bond Ising model:Application to the Fe-Mn-Al alloys[J].Phys.Rev.B,1990,41(7):4774.
[9]Osorio A,Aguirre Contreras W R,Zamora Ligia E,et al.Thermodynamic properties of antiferromagnetic ternary systems using a random-site Ising model[J].Phys.Rev.B,2003,68(2):024420.
[10]Restrepo J,Pérez Alcázar G A.Magnetic properties of Fe0.9-xMn0.1Alxdisordered alloys:Theory[J].Phys.Rev.B,2000,61(9):5880.
[11]Velásquez E A,Duque L F,Mazo-Zuluaga J,et al.Magnetic properties across intergranular region of disordered Fe Mn Al alloys:Theory[J].Physica B,2007,398(2):364.
[12]Vela'squez E A,Mazo-Zuluaga J,Restrepo J,et al.Pseudocritical behavior of ferromagnetic pure and random diluted nanoparticles with competing interactions:Variational and Monte Carlo approaches[J].Phys.Rev.B,2011,83(18):184432.
[13]Pea Lara D,Plascak J A.Mean field renormalization group for Ising models with S≥1[J].Mod.Phys.Lett.B,1996,10(22):1067.
[14]Restrepo J,Greneche J M.Magnetic properties and critical behavior of random Fe Mn Al alloys:An Ising Monte Carlo study[J].Phys.Rev.B,2005,71(6):064406.
[15]Restrepo J,Arnache O.Hysteretic behavior of Fe0.9-q Mn0.1Alqdisordered alloys:a Monte Carlo study[J].Physica B,2002,320(1-4):244.
[16]Restrepo J,Arnache O,Landau D P.Monte Carlo study of the magnetic properties of Fe0.9-qMn0.1Alqdisordered alloys[J].Physica B,2002,320(1-4):239.
[17]Prabodh S,Michael W.Spin-glass behavior in iron-aluminum alloys:A microscopic model[J].Phys.Rev.B,1980,21(1):159.