铁酸铋的热力学势及其相图

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多铁性材料同时具有磁性和极化有序，因而蕴含着丰富的物理内涵和广阔的应用前景。铁酸铋因其室温多铁性，在过去十余年受到广泛关注。然而，其相结构相当复杂，多铁性能的基本物理机制至今仍不完全清楚。一支涵括多位著名学者的国际研究团队，在最新的XRD和中子衍射实验数据基础上，构建了一种新的Landau-Ginzbur热力学势，不仅能定量描述铁酸铋已知行为，还能预测其新型中间结构相变，为绘制多铁性能的铁酸铋相图提供了理论依据，也为揭示多铁性能的基本物理机制奠定了基础。该文近期发表于npj Computational Materials 3:20 (2017); doi:10.1038/s41524-017-0021-3，标题与摘要如下，点击阅读原文可以自由下载论文。

原文链接：

https://www.nature.com/articles/s41524-017-0021-3

Thermodynamic potential and phase diagram for multiferroic bismuth ferrite (BiFeO3) 

Dmitry V. Karpinsky, Eugene A. Eliseev, Fei Xue, Maxim V. Silibin, Alexandra Franz, Maya D. Glinchuk, Igor O. Troyanchuk, Sergey A. Gavrilov, Venkatraman Gopalan, Long-Qing Chen & Anna N. Morozovska

We construct a Landau–Ginzburg thermodynamic potential, and the corresponding phase diagram for pristine and slightly doped bismuth ferrite, a ferroelectric antiferromagnet at room temperature. The potential is developed based on new X-ray and neutron diffraction experiments complementing available data. We demonstrate that a strong biquadratic antiferrodistortive-type coupling is the key to a quantitative description of Bi1−xLaxFeO3 multiferroic phase diagram including the temperature stability of the antiferromagnetic, ferroelectric, and antiferrodistortive phases, as well as for the prediction of novel intermediate structural phases. Furthermore, we show that “rotomagnetic” antiferrodistortive–antiferromagnetic coupling is very important to describe the ferroelectric polarization and antiferrodistortive tilt behavior in the R3c phase of BiFeO3. The Landau–Ginzburg thermodynamic potential is able to describe the sequence of serial and trigger-type phase transitions, the temperature-dependent behavior of the order parameters, and the corresponding susceptibilities to external stimuli. It can also be employed to predict the corresponding ferroelectric and antiferrodistortive properties of Bi1−xLaxFeO3 thin films and nanoparticles by incorporating the gradient and surface energy terms that are strongly dependent on the shape, size, and preparation method.

原文链接：

https://www.nature.com/articles/s41524-017-0021-3

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