HMCSD Simulation on Metaric Spin-Glass Alloys

Metaric 旋转玻璃合金的 HMCSD 模拟

• 批准号: 07640499
• 负责人: MATSUBARA Fumitaka
• 金额: $ 1.41万
• 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: 1995
• 资助国家: 日本
• 起止时间: 1995 至 1996
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-07640499/
• 关键词: Spin-Glass; Dilute Magnetic Alloys; Monte-Carlo Simulation; RKKY Model; Site-Random; Dipole Interaction; 希薄磁性金属; クラスター熱浴法; リエントラント相転移

1. Development of computer simulation algorithmWe have newly developed two simulation methods which are efficient for studying complex systems, especially for spin-glass models : (1) a hybrid Monte-Carlo spin-dynamics (HMCSD) method for the Heisenberg models, and (2) a cluster heat bath (CHB) method for the Ising models.2. Simulation of the Rudermann-Kittel-Kasuya-Yoshida (RKKY) modelMetallic spin-glass alloys are described by using the RKKY model. (1) We have made detailed simulation of the RKKY model and determined the phase diagram of it.(2)We have studied effects of the dipolar interaction on the RKKY model just above its critical consentration and found that, as the temperature is decreased, the magnetization once increases below the Curie temperature then decreases as the temperature is further decreased. We believe this is a key point for reentrant spin-glass phenomena.3. Mixtures of ferromagnetic and antiferromagnetic atomsMixtures of two magnetic atoms are another kind of complex systems for which a spin-glass is expected to occur. We have made computer simulations of both the Ising and Heisenberg models and obtained the following results. (1) In the Ising model, we have found an evidence of the occurrence of the spin-glass phase even for two-dimensions, in contrast with a previous speculation. (2) In the Heisenberg model, we have found a novel magnetic phase in which a longitudinal ferromagnetism and a transverse antiferromagnetism coexist.4. Other frustrated modelsWe have also investigated magnetic structures of various models with some frustrations. Those are a quantum spin systems on the triangular lattice, Ising-like models with competing intaractions, and a ferromagnetic Heisenberg model with dipolar interactions.

1.计算机模拟算法的发展我们发展了两种新的模拟方法，它们对于研究复杂系统，特别是自旋玻璃模型是有效的：（1）用于海森堡模型的混合蒙特-卡罗自旋动力学（HMCSD）方法;（2）用于伊辛模型的团簇热浴（CHB）方法. Rudermann-Kittel-Kasuya-Yoshida（RKKY）模型的模拟用RKKY模型描述了金属自旋玻璃合金。(1)我们对RKKY模型进行了详细的模拟，确定了它的相图。(2)We研究了偶极相互作用对RKKY模型临界浓度以上的影响，发现随着温度的降低，磁化强度在居里温度以下一度增加，然后随着温度的进一步降低而减小。我们相信这是重入自旋玻璃现象的关键点。铁磁和反铁磁原子的混合物两个磁性原子的混合物是另一种预计会发生自旋玻璃的复杂系统。我们对伊辛模型和海森堡模型进行了计算机模拟，得到了以下结果。(1)在伊辛模型中，我们发现了即使在二维情况下也存在自旋玻璃相的证据，这与以前的推测相反。(2)在海森伯模型中，我们发现了一个新的磁相，其中纵向铁磁性和横向反铁磁性共存.我们还研究了各种模型的磁结构，但都有一些挫折。这三个模型分别是三角晶格上的量子自旋系统、具有竞争相互作用的类伊辛模型和具有偶极相互作用的铁磁海森堡模型。

项目成果

Fumitaka Matsubara and Takayuki Shirakura: "Phase Transition in Site-Random Spin Glass Models" Journal of the Physical Society of Japan Computational Physics as a New Frontier in Condn. Matter Research. 221-229 (1995)

Fumitaka Matsubara 和 Takayuki Shirakura：“位点随机自旋玻璃模型中的相变”日本物理学会杂志计算物理学作为 Condn 的新前沿。

Junya Sasaki and Fumitaka Matsubara: "Circular Phase of a Two-Dimensional Ferromagnet with Dipolar Interactions" Journal of the Physical Society of Japan. (in press).

Junya Sasaki 和 Fumitaka Matsubara：“具有偶极相互作用的二维铁磁体的循环相位”日本物理学会杂志。

Fumitaka Matsubara: "Anisotropic Ferromagnel on a Triangular Lattice with Antiterromagnetic Next-Nearest-Neighbor Interactions" Journal of the Physical Society of Japan. 65. 1399-1403 (1996)

Fumitaka Matsubara：“具有反铁磁次近邻相互作用的三角形晶格上的各向异性铁磁体”日本物理学会杂志。

Fumitaka Matsubara: "Phase diagram of the S=1/2 quantum an titerromagnetic XY model on the trianglar lattice in magnetic fields" Rhysical Review B. (印刷中). (1997)

Fumitaka Matsubara：“磁场中三角晶格上的 S=1/2 量子铁磁性 XY 模型的相图”Rhysical Review B.（出版中）。

F.Matsubara, T.tamiya, and T.Shirakura: "Mixed Phase of a Longitudinal Ferromagnetism and a Transverse Antiferromagnetism in a Site-Random Heisenberg Model" Physical Review Letters. Vol.77, No.2. 378-381 (1996)

F.Matsubara、T.tamiya 和 T.Shirakura：“随机海森堡模型中纵向铁磁性和横向反铁磁性的混合相”物理评论快报。