Abstract

Phase transitions in multiferroics with spatially modulated structures as ground states are studied in this work. The key physical mechanisms needed to implement modulated states of various kinds (cycloidal and helicoidal magnetic phases) and the conditions of phase transitions within modulated states are discussed. The domain of physical parameters where the ground state of the spin cycloid becomes unstable is determined for single crystals and films of bismuth ferrite. It is demonstrated that the domains of existence and stability of spin cycloids differ. Analytical estimates of their boundaries are obtained. The behavior of the spin system in a (110) BiFeO₃ film in the magnetic field is studied, and diagrams of the ground magnetic states are plotted.

中文翻译：

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摆线自旋有序的多铁磁自旋取向转变

摘要

在这项工作中研究了具有空间调制结构作为基态的多铁磁中的相变。讨论了实现各种调制状态（摆线和螺旋磁相）所需的关键物理机制以及调制状态内的相变条件。对于单晶和铋铁氧体薄膜，确定了自旋摆线的基态变得不稳定的物理参数范围。证明自旋摆线的存在域和稳定性域不同。获得其边界的分析估计。研究了自旋系统在（110）BiFeO ₃薄膜中在磁场中的行为，并绘制了基态磁态图。