Laboratoire Structures, Propriétés et Modélisation des Solides, CNRS-UMR 8580, Ecole Centrale Paris, Châtenay-Malabry, France.
Phys Rev Lett. 2011 Jun 10;106(23):237601. doi: 10.1103/PhysRevLett.106.237601.
Density-functional calculations are performed to predict structural and magnetic properties of (001) BiFeO(3) films under tensile epitaxial strain. These films remain monoclinic (Cc space group) for misfit strains between 0% and ≈8%, with the polarization, tilt axis and magnetization all rotating when varying the strain. At a tensile strain ≈8%, these films undergo a first-order phase transition towards an orthorhombic phase (Ima2 space group). In this novel phase, the polarization and tilt axis lie in the epitaxial plane, while the magnetization is along the out-of-plane direction and the direction of the antiferromagnetic vector is unchanged by the phase transition. An unexpected additional degree of freedom, namely, an antiphase arrangement of Bi atoms, is also found for all tensile strains.
采用密度泛函理论计算预测了拉伸外延应变下（001）BiFeO3 薄膜的结构和磁性能。当应变变化时，这些薄膜在 0%到 ≈8%的失配应变范围内仍然保持单斜（Cc 空间群），极化、倾斜轴和磁化都发生旋转。在拉伸应变为 ≈8%时，这些薄膜经历了向正交相（Ima2 空间群）的一级相变。在这个新相中，极化和倾斜轴位于外延平面内，而磁化沿垂直于外延平面的方向，并且磁矢量的反铁磁方向在相变过程中保持不变。还发现了一个意想不到的额外自由度，即所有拉伸应变下的 Bi 原子反相排列。
