超薄膜磁性材料上XY模型的临界现象

采用经典XY模型，阐明了三角格子上层状超薄膜磁性材料的相变和临界现象.并用Monte-Carlo方法对该模型的内部能量、比热、chirality等热力学量进行了计算.使用finite-size scaling 分析法对临界现象的性质进行了论述.通过上述分析和计算，发现该模型在反强磁性层与强磁性层内的chirality在一定范围内随温度的变化急剧增加，这是一种新的chirality相变；而在另一范围内存在Kosterliz-Thouless相变和通常的chirality相变.这种新的chirality相变的 关键词： 层状XY模型 临界现象 Monte-Carlo模拟 磁性薄膜

Phase transitions of XY model in ultra-thin magnetic film with a triangular latt ice

Phase transitions and critical phenomena have been clarified for an XY model on the triangular lattice of ultra-thin magnetic films. We have calculated the ther modynamic quantities such as the internal energy, the specific heat, the chirali ty and so on by using Monte-Carlo simulations. The critical behaviours have been clarified by using finite-size scaling analyses. We have found a new critical b ehaviour due to a steep increase of the chirality as a function of temperature f or the XY model on a layered triangular lattice with antiferromagnetic layers an d ferromagnetic layers in some range of interaction parameters, besides the Kost erlize-Thouless transition and the usual chirality transition. In the new chiral ity transition, the value of a critical exponent has not been observed over any thickness dependence of this value as far as the layered systems are concerned. In the other chirality transition, the value of a critical exponent has been obs erved over the thickness.