The Ginzburg–Landau method is used to conduct a phenomenological analysis of how the sample thickness impacts the incommensurate spin states in the TbMnO3 centrosymmetric ferroelectromagnet. The analysis is performed using the first-harmonic approximation, and provides a qualitative confirmation of the experimentally observed decrease in the film modulation vector at a decreasing temperature, as well as an increase in the vector as the film thickness decreases at a constant temperature. The effect that the film thickness has on the first- and second-order phase transition lines is analyzed, and the tendency of the incommensurate spin phase volume to decrease with a decrease in the film thickness is demonstrated.

中文翻译：

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薄膜厚度对锰酸铽调制自旋结构的影响

Ginzburg-Landau 方法用于对样品厚度如何影响 TbMnO3 中心对称铁电磁体中的非公称自旋态进行现象学分析。该分析是使用一次谐波近似进行的，并提供了对实验观察到的薄膜调制矢量在温度降低时减少的定性确认，以及在恒定温度下随着薄膜厚度减小而增加的矢量。分析了薄膜厚度对一阶和二阶相变线的影响，证明了不公度自旋相体积随着薄膜厚度的减小而减小的趋势。