Magnetic Dipolar Interactions and Reentrant Spin-Glass Transition

磁偶极相互作用和重入自旋玻璃转变

• 批准号: 16540335
• 负责人: MATSUBARA Fumitaka
• 金额: $ 2.05万
• 依托单位: Tohoku University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 2004
• 资助国家: 日本
• 起止时间: 2004 至 2006
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-16540335/
• 关键词: Spin-Glass; Reentrant Spin-Glass; Dilute Ferromagnet; Monte Carlo Simulation; Genetic Algorism; リエントラント相転移; モンテカルロ・シミュレーション; 希釈磁性体; 磁気双極子相互作用; 双極子相互作用; 基底状態

Reentrant spin-glass (RSG) transition is a well-known phenomenon of spin glasses (SGs). However, the mechanism responsible for the RSG transition has not yet been resolved. In this project, we found for the first time a realistic model which reproduces the RSG phenomena and studied the mechanism responsible to the RSG transition.1. RSG ModelWe considered the magnetic ordering of a dilute ferromagnetic (FM) Heisenberg model AxBi-x (0<x<l) with antiferromagnetic next-nearest neighbor interactions, where A is a ferromagnetic atom and B a non-magnetic atom. We performed a large scale Monte Carlo simulation of the model with x~0.8 on various sizes of the LXLXL lattice and found that the model reproduces the RSG transition. That is, as the temperature is decreased, the magnetization increases rapidly below a certain temperature, reaches a maximum value, then ceases at some lower temperature. The low temperature phase was suggested to be a SG phase that is characterized by ferromagnetic clust … More ers. Then having performed the same simulation for various x, we determined a "concentration(x)-temperature(7) phase diagram"of the model. We applied the model to study the phase diagram of EuxSri-xS, which is an experimental realization of the model.2. RSG Transition and Fluctuating ClustersWe examined the RSG transition in the dilute FM model. We calculated the site magnetization having developed a novel simulation algorism that removes uniform rotation of the spins. Results showed that clusters of fluctuating spins exist in the FM phase. As the temperature is decreased, the spins in those clusters freeze and the FM long-range order breaks to ferromagnetic clusters. These results are compatible with experimental observations. The fluctuating clusters appear in domains with lower spin concentrations. Hence we suggested that the RSG transition comes from a scattering of local concentration of the magnetic atoms.3. Genetic Algorism for Heisenberg ModelsWe developed a genetic algorism for Heisenberg model having generalized Pal's genetic algorism for the Ising SG. The algorism was used to analyze the ground state properties of the dilute model. Less

重入自旋玻璃（RSG）转变是自旋玻璃（SG）的一种常见现象。然而，负责RSG过渡的机制尚未解决。在本项目中，我们首次建立了一个真实的RSG模型，再现了RSG现象，并研究了RSG转变的机理. RSG模型我们考虑了具有反铁磁次近邻相互作用的稀铁磁（FM）Heisenberg模型AxBi-x（0<x<1）的磁序，其中A是铁磁原子，B是非磁原子.我们在不同尺寸的LXLXL晶格上对x~0.8的模型进行了大规模Monte Carlo模拟，发现模型再现了RSG跃迁。也就是说，随着温度降低，磁化强度在低于某一温度时迅速增加，达到最大值，然后在某一较低温度时停止。低温相为SG相，具有铁磁性 ...更多信息 呃。然后对不同的x进行相同的模拟，我们确定了模型的“浓度（x）-温度（7）相图“。应用该模型研究了EuxSri-xS的相图，这是该模型的实验实现. RSG跃迁与涨落我们研究了稀FM模型中的RSG跃迁。我们计算的网站磁化开发了一种新的模拟算法，消除了均匀旋转的自旋。结果表明，在FM相中存在自旋涨落的团簇。随着温度的降低，这些团簇中的自旋冻结，FM长程有序断裂成铁磁团簇。这些结果与实验观察相符。涨落团簇出现在自旋浓度较低的区域。因此，我们认为RSG跃迁来自于磁性原子局域浓度的散射.海森伯模型的遗传算法本文将Ising SG的遗传算法推广到海森伯模型，提出了一种海森伯模型的遗传算法。利用该算法分析了稀模型的基态性质。少

项目成果

Phase diagram of a dilute ferromagnet model with antiferromagnetic next-nearest-neighbor-interactions

具有反铁磁次最近邻相互作用的稀铁磁体模型的相图

• 发表时间: 2005
• 期刊: Physical Review B 72
• 作者: Y.M.Zhai;I.Z.Kiss;H.Daido;J.L.Hudson;H.Daido;H.Daido;原科浩;原科 浩;H.Harashina;S.Ohigashi;Daisuke Ninomiya;F.Matsubara;S.Niidera;S.Ohigashi;Fumitaka Matsubara;F.Matsubara;S.Niidera;T.Ohigashi;S.Niidera;鈴木伸夫;S.Abiko;S.Niidera
• 通讯作者: S.Niidera

and Takayuki Shirakura Monte Carlo Simulation of the ±J Heisenberg Model in Parisi State

和 Takayuki Shirakura 巴黎州 ±J 海森堡模型的蒙特卡罗模拟

• 发表时间: 2005
• 期刊: Progress of Theoretical Physics Supplement No. 157
• 作者: Y.M.Zhai;I.Z.Kiss;H.Daido;J.L.Hudson;H.Daido;H.Daido;原科浩;原科 浩;H.Harashina;S.Ohigashi;Daisuke Ninomiya;F.Matsubara;S.Niidera;S.Ohigashi;Fumitaka Matsubara;F.Matsubara;S.Niidera;T.Ohigashi;S.Niidera;鈴木伸夫;S.Abiko;S.Niidera;Fumitaka Matsubara;Takayuki Shirakura;Nobuo Suzuki;S.Abiko;S.Niidera;Fumitaka Matsubara
• 通讯作者: Fumitaka Matsubara

Ground state and low-lying excitations in a Heisenberg spin-glass model in three dimensions

三维海森堡自旋玻璃模型中的基态和低位激发

• 发表时间: 2004
• 期刊: Physical Review B 70・17
• 作者: M.Igarashi;T.Kodaira;T.Shimizu;A.Goto;K.Hashi;T.Shirakura;F.Matsubara;T.Shirakura et al.;F.Matsubara et al.;T.Shirakura;F.Matsubara;F.Matsubara;F.Matsubara
• 通讯作者: F.Matsubara

H-T phase diagram of a 3D Heisenberg spin glass

3D 海森堡自旋玻璃的 H-T 相图

• 发表时间: 2007
• 期刊: Journal of Magnetism and Magnetic Materials 310
• 作者: Y.M.Zhai;I.Z.Kiss;H.Daido;J.L.Hudson;H.Daido;H.Daido;原科浩;原科 浩;H.Harashina;S.Ohigashi;Daisuke Ninomiya
• 通讯作者: Daisuke Ninomiya

Monte Carlo Simulation of the $pm J$ Heisenberg Model in Parisi State

帕里西州 $pm J$ 海森堡模型的蒙特卡罗模拟

• 发表时间: 2005
• 期刊: Progress of Theoretical Physics Supplement No.157
• 作者: Y.M.Zhai;I.Z.Kiss;H.Daido;J.L.Hudson;H.Daido;H.Daido;原科浩;原科 浩;H.Harashina;S.Ohigashi;Daisuke Ninomiya;F.Matsubara;S.Niidera;S.Ohigashi;Fumitaka Matsubara;F.Matsubara;S.Niidera;T.Ohigashi;S.Niidera;鈴木伸夫;S.Abiko;S.Niidera;Fumitaka Matsubara
• 通讯作者: Fumitaka Matsubara