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arXiv 1111.2927cond-mat.stat-mech
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自旋-S(S<=1)稀Ising铁磁体的新有效场论

A new effective field theory for spin-S (S<=1) dilute Ising ferromagnets

Ümit Akıncı, Yusuf Yüksel, Hamza Polat

摘要:

站点稀释自旋1/2伊辛和自旋1布鲁姆Capel(BC)模型中存在的横向场相互作用的检查,通过引入有效场近似,考虑到多站点的相关性在考虑的晶格与改进的组态平均技术的集群。临界浓度以下的转变温度降低到零的确定为两个模型,并与文献中的其他方法获得的估计值进行了比较。研究发现,非磁性原子对晶格位置的稀释可能会导致模型某些特征的剧烈变化。特别注意了自旋为1的BC模型的全局相图,并指出系统中二阶重入的发生条件相当复杂,因为重入的存在或熄灭对D/J,Ω/J和c之间的竞争效应相当敏感。

英文摘要:

Site diluted spin-1/2 Ising and spin-1 Blume Capel (BC) models in the presence of transverse field interactions are examined by introducing an effective-field approximation that takes into account the multi-site correlations in the cluster of a considered lattice with an improved configurational averaging technique. The critical concentration below which the transition temperature reduces to zero is determined for both models, and the estimated values are compared with those obtained by the other methods in the literature. It is found that diluting the lattice sites by non magnetic atoms may cause some drastic changes on some of the characteristic features of the model. Particular attention has been paid on the global phase diagrams of a spin-1 BC model, and it has also been shown that the conditions for the occurrence of a second order reentrance in the system is rather complicated, since the existence or extinction of reentrance is rather sensitive to the competing effects between D/J, Ω/J and c.

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