Mechanisms for multiferroicity in rare-earth orthoferrites: Role of the Dzyaloshinskii-Moriya interaction

该项目的目的是确定负责多铁性材料中磁和铁电序参数之间耦合的微观机制，其中铁电性是由磁有序（II型多铁性）引起的。特别注意的是，将支付到的反对称Dzyaloshinskiii-Moriya（DM）的相互作用，这被认为是负责的多铁性的主要组成部分之一的作用的阐明。澄清的起源之间的耦合的磁性和铁电序参数将允许创建新的功能材料与所需的properties.We计划研究的晶体和磁性结构和磁相互作用的稀土正铁氧体RFeO 3（R = Ho，Dy，Lu，Tb和Tm）。各种中子散射技术计划应用于RFeO 3家族成员的晶体和磁性的调查。将通过极化中子衍射研究其复杂磁结构的特性及其在温度、磁场和电场等外部条件下的演变，包括独特的球形中子极化技术以及经典的翻转比方法。磁动力学的调查将通过非弹性中子散射，它允许获得磁交换相互作用参数。RFeO 3晶体结构的详细研究，即在弱铁磁相的结构扭曲，以证明预期的对称性降低的搜索将通过非极化中子和X射线衍射技术以及衍射测量来完成。建议的实验研究的结果将分析这些材料的铁电相。基于所获得的结果，磁电相互作用模型负责的多铁性在正铁酸盐将开发和它的普遍性水平将建立。

The aim of this project is to determine the microscopic mechanisms responsible for the coupling between the magnetic and ferroelectric order parameters in multiferroic materials, where ferroelectricity is induced by magnetic ordering (type-II multiferroics). Particular attention will be paid to the elucidation of the role of the antisymmetric Dzyaloshinskii-Moriya (DM) interaction which is considered to be one of the main components responsible for the multiferroicity. Clarification of the origin of the coupling between the magnetic and ferroelectric order parameters would allow to create new functional materials with desired properties.We plan to study the crystal and magnetic structures and magnetic interactions in rare-earth orthoferrites RFeO3 (R = Ho, Dy, Lu, Tb and Tm). Various neutron scattering techniques are planned to be applied for the investigation of crystal and magnetic properties of the RFeO3 family members. The peculiarities of their complex magnetic structures and their evolution under external conditions, such as temperature, magnetic and electric fields will be studied by polarized neutron diffraction, including both the unique spherical neutron polarimetry technique as well as the classical flipping-ratio method. Investigations of the magnetic dynamics will be performed by means of inelastic neutron scattering, which allows to obtain the magnetic exchange interaction parameters. Detailed studies of RFeO3 crystal structures, namely the search for structural distortions in a weak ferromagnetic phase to demonstrate the expected symmetry lowering will be done by both unpolarized neutron and X-ray diffraction techniques as well as dilatometry measurements. Results of the proposed experimental studies will be analyzed in relation to the ferroelectric phases of these materials. Based on the obtained results, the model of magnetoelectric interactions responsible for the multiferroic properties in orthoferrites will be developed and its level of universality will be established.