旋磁耦合对反铁畸变反铁磁体磁性能的影响
Rotomagnetic couplings influence on the magnetic properties of antiferrodistortive antiferromagnets
摘要：
在Landau-Ginzburg-Devonshire（LGD）唯象理论的框架内，我们考虑了在外加磁场和电场的情况下，通过双二次旋磁耦合来控制顺电反铁磁体性质的可能性.我们使用EuTiO 3作为原型，具有相对公知的材料参数。令人惊讶的强烈影响，这种耦合几乎所有的属性，没有外部的字段中获得的温度区域与共存的反铁磁和反铁扭曲相，即在多铁性状态。特别是，所观察到的尼尔温度TN（5.5 K）被证明是由旋磁耦合定义的，而没有这种耦合TN似乎要高得多（26 K）。当旋磁耦合常数值较小时，反铁磁相变级数分别为二级或一级。预测了旋磁耦合对磁和介电常数的形式和数值的本质影响。旋磁耦合和旋电耦合开辟了通过施加外部磁场或电场来控制相图形式的额外途径。电场的临界值（反铁磁到铁磁相变）出现基本上小于一个计算没有旋磁耦合，可以是重要的应用程序。
英文摘要：
Within the framework of Landau-Ginzburg-Devonshire (LGD) phenomenological theory we consider the possibility to control properties of paraelectric antiferromagnets via biquadratic rotomagnetic coupling with and without external magnetic and electric field application. We use EuTiO3 as a prototype with relatively well-known material parameters. Surprisingly strong influence of this coupling practically on all the properties without external fields was obtained in the temperature region with coexistence of antiferromagnetic and antiferrodistorted phases i.e. in multiferroic state. In particular, the observed Neel temperature TN (5.5 K) was shown to be defined by rotomagnetic coupling, while without this coupling TN appeared to be much higher (26 K). For small or high enough rotomagnetic coupling constant value the antiferromagnetic phase transition order appeared to be the second or the first order respectively. The essential influence of rotomagnetic coupling on the form and value of magnetic and dielectric permittivity was also forecasted. The rotomagnetic coupling along with rotoelectric one opens the additional way to control the form of the phase diagrams by application of external magnetic or electric field. The critical value of the electric field (for antiferromagnetic to ferromagnetic phase transition) appeared essentially smaller than the one calculated without rotomagnetic coupling that can be important for applications.
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