共查询到19条相似文献,搜索用时 109 毫秒
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二维超晶格伊辛模型的实空间重正化群计算 总被引:2,自引:1,他引:1
我们在Mignal-Kadanoff重正化群近似下运用非整数标度变换来计算二维超晶格伊辛系统的临界性质。我们发现存在两个临界温度和三个相,并讨论了与各向异性参量有关的临界指数。 相似文献
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Blume–Emery–Griffiths纳米管的热力学与相变性质 总被引:1,自引:0,他引:1
利用有效场理论研究了圆柱形纳米管上Blume-Emery-Griffiths系统的热力学与相变性质,得到了系统的磁化强度、磁化率、比热和相图.讨论了四次交换作用与二次交换作用的比值 与晶格场对系统热力学量和相图的影响.研究发现:系统存在三临界点,且三临界点由参数 和晶格场共同决定,即若确定了参数 ,则三临界点所对应的晶格场也能确定.随着参数 的增加,系统出现三临界点时所对应的温度和晶格场也相应增大. 相似文献
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《原子与分子物理学报》2017,(3)
利用有效场理论研究了柱形纳米管上Blume-Emery-Griffiths系统的热力学与相变性质,得到了系统的磁化强度、磁化率、比热和相图.讨论了四次交换作用与二次交换作用的比值r与晶格场对系统热力学量和相图的影响.研究发现:系统存在三临界点,且三临界点由参数r和晶格场共同决定,即若确定了参数r,则三临界点所对应的晶格场也能确定.随着参数r的增加,系统出现三临界点时所对应的温度和晶格场也相应增大. 相似文献
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利用等效变换和重正化群变换的方法,在Sierpinskigasket晶格上研究了具有近邻和次近邻相互作用Gaussian模型的临界性质,求出了临界温度和关联长度临界指数.结果表明:在相变点近邻相互作用K1和次近邻相互作用K2之间满足一定的关系,这种关系对铁磁体和反铁磁体都适用.并且考虑次近邻相互作用后,临界温度和临界指数都不发生改变. 相似文献
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本利用平均场近似,研究了负UK伯德模型中η对超导体的热力性质,给出了临界磁场与温度的关系,式,求出临界温度处的比热跃迁,它们与已知的实验符合行比较好。 相似文献
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S. V. Belim 《Journal of Experimental and Theoretical Physics》2004,98(2):316-321
A field-theoretic approach is applied to describe behavior of three-dimensional, weakly disordered, elastically isotropic, compressible systems with long-range interactions at various values of a long-range interaction parameter. Renormalization-group equations are analyzed in the two-loop approximation by using the Padé-Borel summation technique. The fixed points corresponding to critical and tricritical behavior of the systems are determined. Elastic deformations are shown to changes in critical and tricritical behavior of disordered compressible systems with long-range interactions. The critical exponents characterizing a system in the critical and tricritical regions are determined. 相似文献
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R. Folk 《Phase Transitions》2013,86(4):645-666
Solid state systems exhibit besides usual second order phase transitions a rich variety of multicritical phenomena like Lifshitz points (or lines), tricritical points (or lines) and even tricritical Lifshitz points. Realizations of such points are numerous and were also verified in the family of ferroelectrics of the type (PbySn1y)2P2(SexS1-x)6. A review of the critical behavior at such points is presented here. Because of the importance of the uniaxial dipolar interaction in ferroelectrics the critical behavior is different from systems with short range interaction only. Moreover the coupling to the elastic degrees of freedom may not be neglected, and leads under certain conditions to a critical temperature dependence in certain elastic constants. Crossover phenomena, which are expected in the experimental accessible region of experiments are also considered. 相似文献
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Hu CD 《J Phys Condens Matter》2012,24(8):086001
The Dzyaloshinskii-Moriya (DM) interaction in metals is an important mechanism for many magnetic properties. We start with the s-d exchange model and spin-orbit interaction for weak itinerant ferromagnetic systems to establish the form of DM interaction for metallic magnetic systems. The s-d exchange interaction is treated accurately and the conduction electron-mediated magnetism gives a form of DM interaction which is different from that in insulators. The implications of our result to spiral spin states and skyrmion lattices are also discussed. 相似文献
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We investigate the thermodynamic properties of double chains of Ising and spherical spins with different first and a crossed second neighbour interaction in zero field. The interest is focussed on the region where different ground states are nearly degenerate due to competing interaction constants. The Ising system shows quasi-singular behaviour of the susceptibility for certain ratios of parameters. Moreover the nearest neighbour correlation function exhibits a sharp crossover from high-temperature “compensation-point” to low temperature ferro- or antiferromagnetic behaviour. An analogy is found between compensation points and tricritical points of higher dimensional systems. 相似文献
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《Physica A》1988,152(3):343-358
Within an effective-field approximation, general expressions for evaluating the second-order phase transition line and the tricritical point of the anisotropic Blume-Emery-Griffiths model are obtained by the use of the differential operator technique. The phase diagrams and the behavior of the tricritical point are investigated numerically for the honeycomb lattice (z = 3) and square lattice (z = 4). We find a new disordered phase which may correspond to the staggered quadrupolar phase predicted in the Monte Carlo simulation, when some conditions are satisfied. The phase diagrams for z = 3 and z = 4 systems exhibit a reentrant behavior for positive values of the uniaxial anisotropy parameter. The change of the tricritical point with the value of the reduced biquadratic parameter is also studied for the system with z = 3. 相似文献
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研究了以带有Dzyaloshinski-Mariya(DM)相互作用的两比特自旋体系为工质的量子纠缠Otto热机和量子Stirling热机.两种不同热机在各自的循环过程中,通过保持其他参量不变,只有DM相互作用发生改变,从而分析热机循环中DM相互作用与热传递、做功以及效率等热力学量之间的关系.研究结果表明:DM相互作用对两种热机的基本量子热力学量都具有重要的影响,但量子Stirling热机由于回热器的使用,其循环效率会大于量子Otto纠缠热机的效率,甚至会超过Carnot效率;得到了量子Otto纠缠热机和量子Stirling热机做正功的条件.因此,在这两个纠缠体系中,热力学第二定律都依然成立. 相似文献
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A novel electron spin-reorientation transition is discovered by 13C NMR in the quasi-two-dimensional organic antiferromagnet kappa-(BEDT-TTF)(2)Cu[N(CN)(2)]Cl. The spin reorientation occurs as an external field is swept through the orientation of the characteristic vector of the Dzialoshinskii-Moriya (DM) interaction, thus providing a precise determination of the orientation of the DM vector. Such a spin reorientation could help to characterize the DM interaction in other antiferromagnetic systems. 相似文献