تقرير
Ising spin glass under continuous-distribution random magnetic fields: Tricritical points and instability lines
| العنوان: | Ising spin glass under continuous-distribution random magnetic fields: Tricritical points and instability lines |
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| المؤلفون: | Crokidakis, N., Nobre, F. D. |
| المصدر: | Phys. Rev. E 77, 041124 (2008) |
| سنة النشر: | 2008 |
| المجموعة: | Condensed Matter |
| مصطلحات موضوعية: | Condensed Matter - Statistical Mechanics |
| الوصف: | The effects of random magnetic fields are considered in an Ising spin-glass model defined in the limit of infinite-range interactions. The probability distribution for the random magnetic fields is a double Gaussian, which consists of two Gaussian distributions centered respectively, at $+H_{0}$ and $-H_{0}$, presenting the same width $\sigma$. It is argued that such a distribution is more appropriate for a theoretical description of real systems than its simpler particular two well-known limits, namely the single Gaussian distribution ($\sigma \gg H_{0}$), and the bimodal one ($\sigma = 0$). The model is investigated by means of the replica method, and phase diagrams are obtained within the replica-symmetric solution. Critical frontiers exhibiting tricritical points occur for different values of $\sigma$, with the possibility of two tricritical points along the same critical frontier. To our knowledge, it is the first time that such a behavior is verified for a spin-glass model in the presence of a continuous-distribution random field, which represents a typical situation of a real system. The stability of the replica-symmetric solution is analyzed, and the usual Almeida-Thouless instability is verified for low temperatures. It is verified that, the higher-temperature tricritical point always appears in the region of stability of the replica-symmetric solution; a condition involving the parameters $H_{0}$ and $\sigma$, for the occurrence of this tricritical point only, is obtained analytically. Some of our results are discussed in view of experimental measurements available in the literature. Comment: 23 pages, 8 figures, accept for publication in Phys. Rev. E |
| نوع الوثيقة: | Working Paper |
| DOI: | 10.1103/PhysRevE.77.041124 |
| URL الوصول: | http://arxiv.org/abs/0804.1342 |
| رقم الأكسشن: | edsarx.0804.1342 |
| قاعدة البيانات: | arXiv |
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