中文摘要：

在关联有效场理论的框架内，利用微分算子技术，详细地计算了基于横场伊辛模型描述的对称铁电薄膜系统的相变性质．根据薄膜各层自旋平均值构成的一系列耦合方程，推导出可以用来计算任意层的具有不同表面层的薄膜相图的解析通式方程，讨论了参数修改对薄膜相互作用参数从FPD（铁电相占主导地位的相图）到PPD（顺电相占主导地位的相图）过渡值和参数空间中各相变区域的影响．在与平均场近似进行比较的结果显示，关联有效场理论所得到的铁电薄膜的铁电性在某种程度上比平均场近似下的结果减弱．

英文摘要：

Within the framework of effective-field theory with correlations, phase transition properties of ferroelectric thin films with differ- ent symmetrical surfaces described by the spin-l/2 transverse field Ising model are studied systematically by the differential operator technique. According to the coupling equations with the layer polarization average, the analytical general equations for phase dia- grams of multiple-surface ferroelectric thin films with different surface layers have been derived. Then, effects of various parameter modifications on the crossover values from the FPD （ferroelectric-dominant phase diagram） to the PPD （paraelectric-dominant phase diagram） and phase transition regions in the parameter space are discussed in detail. In comparison with the mean-field approximation, the results indicate that the effective-field theory with correlations maybe reduce the ferroelectricity of the ferroelectric thin films more exaggeratedly than the mean-field approximation to some extent.