Study on the Magnetic Dilution in Quantum Spin Systems

量子自旋系统中的磁稀释研究

• 批准号: 08640491
• 负责人: IDOGAKI Toshihiro
• 金额: $ 1.02万
• 依托单位: KYUSHU UNIVERSITY
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 1996
• 资助国家: 日本
• 起止时间: 1996 至 1997
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-08640491/
• 关键词: Magnetic dilution; Qunatum soin; Effective field theory; Critical concentration; Curie temperature; Ising nodel; Heisenberg model; Biquadratic exchange interaction; キュリー濃度

(1) Selective Magnetic Dilution and Site PercolationThe selective magnetic dilution has been studied by the new effective field theory (NEFT) on the lattices with several kinds of two-sublattice structures. Sublattices A and B are assumed to be randomly but selectively diluted by non magnetic atoms, keeping dilution ratio U=(1-p_B)/(1-p_A) constant, and the global phase diagrams of T_C(p_A, p_B) has been calculated. In conjunction with the phase diagram at T=OK,we investigated selective site percolation of this system by real space renormalization group theory and clarified the role of site selectivity U in the study of thecorrelation length exponent and the fractal dimension of the incipient percolation cluster.(2) An Effective Field Theory for Dilute Anisotropic Heisenberg FerromagnetsDilute anisotropic Heisenberg ferromagnets have been studied by NEFT based on a two-site cluster approximation with an Ising character assumed for the surrounding spins. The results for the Curie temper … More ature, T_C, and the critical concentration for magnetic ordering are improvements on those of a single-site approximation where the exchange anisotropy cannot be accounted for. The initial reduction in T_C with dilution has been confirmed to decrease with increase in both the lattice coordination number and exchange anisotropy.(3) Bilinear-Biquadratic Quantum Exchange Model with Single-Ion Uniaxial AnisotropyThe above calculation has been extended to the system of spin S=1, including biquadratic exchange interaction J' and single ion anisotropy D.In particular, we studied the cross-over from anisotropic Ising to isotropic Heisenberg behavior in the variation of T_C with strength J', and also discussed about a spurious reentrant transition phenomena which is found in the vicnity of the critical concentration over a range of strength D.For the isotropic case of D=0, we showed rigorously that the ground state of the Hamiltonian is always singlet on a connected finite lattice with an even number of site, if the exchange interactions satisfy the condition J'>J>0. Less

（1）选择性磁性稀释和位点渗透，选择性磁性稀释已通过新的有效田间理论（NEFT）在具有几种两种两种共同结构的晶格上进行了研究。假定sublattices A和B随机但被非磁原子选择性稀释，保持稀释比u =（1-p_b）/（1-p_a）常数，并且已经计算了T_C（P_A，P_B）的全局相图。 In conjunction with the phase diagram at T=OK, we investigated selective site membership of this system by real space regenerative group theory and clarified the role of site selectivity U in the study of the correlation length exponent and the fractal dimension of the incipient membership cluster.(2) An Effective Field Theory for Dilute Anisotropic Heisenberg FerromagnetsDilute anisotropic Heisenberg已经通过NEFT研究了Ferromagnet，基于两个站点簇的近似值，并为周围的旋转假定具有ISING特征。居里温度的结果……更多的ature，t_c和磁性排序的临界浓度是无法解释交换各向异性的单个位点近似值的结果。已经证实，T_C的最初减少已证实随着晶格配位数和交换各向异性的增加而减少。（3）双线性 - 骨化量子交换模型，具有单离子单位各向异性的上述计算已将上述计算扩展到旋转系统= 1的系统，包括生物交换的系统，包括生物量交换j''和单次交换j'''''inis ion and ion and ion and in Ion and D.在T_C变化中与强度j'的各向同性海森堡行为的各向异性，还讨论了关于在一系列强度范围的临界浓度的危险中发现的杂乱无章的过渡现象。如果交换交互满足条件J'> j> 0。较少的

项目成果

A.Tanaka, Y.Miyoshi, T.Idogaki: "A Study on the Magnetically Dilute Anisotropic Heisenberg Ferromagnet II" Tech.Rep.of Kyushu University. Vol.69, No.6. 733-740 (1996)

A.Tanaka、Y.Miyoshi、T.Idogaki：“磁稀释各向异性海森堡铁磁体 II 的研究”九州大学技术代表。

T.Idogaki, A.Tanaka, J.W.Tucker: "Bilineae-biquadratic quantum exchange model with single-ion uniaxial anisotropy" Jour.Magn.Magn.Mater.(in press). (1998)

T.Idogaki、A.Tanaka、J.W.Tucker：“具有单离子单轴各向异性的双线性双二次量子交换模型”Jour.Magn.Magn.Mater.（​​正在出版）。

A.Tanaka,T.Idogaki: "Singlet ground state of the bilinear-biquadratic exchange Hamiltonian" Phys.Rev.B. Vol.56 No.17. 10774-10777 (1997)

A.Tanaka，T.Idogaki：“双线性双二次交换哈密顿量的单线基态”Phys.Rev.B。

T.Idogaki,Y.Miyoshi,J.W.Tucker: "An effective field theory for dilute anisotropic Heisenberg ferromagnets" Jour.Magn.Magn.Mater.Vol.154 No.2. 221-230 (1996)

T.Idogaki、Y.Miyoshi、J.W.Tucker：“稀释各向异性海森堡铁磁体的有效场理论”Jour.Magn.Magn.Mater.Vol.154 No.2。

田中彰則,三好雄司,井戸垣俊弘: "異方的ハイゼンベルグ強磁性体の磁気希釈に関する研究II" 九州大学 工学集報. 第69巻 第6号. 733-740 (1996)

Akinori Tanaka、Yuji Miyoshi、Toshihiro Idogaki：“各向异性海森堡铁磁体的磁稀释研究 II”九州大学工学通报，第 69 卷，第 6 期，733-740 (1996)