1] Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093, China [2] Department of Physics, Southeast University, Nanjing 211189, China.
Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093, China.
Sci Rep. 2014 Oct 6;4:6530. doi: 10.1038/srep06530.
One of the core issues for multiferroicity is the strongly coupled ferroelectric polarization and magnetization, while so far most multiferroics have antiferromagnetic order with nearly zero magnetization. Magnetic spinel compounds with ferrimagnetic order may be alternative candidates offering large magnetization when ferroelectricity can be activated simultaneously. In this work, we investigate the ferroelectricity and magnetism of spinel FeCr2S4 in which the Fe(2+) sublattice and Cr(3+) sublattice are coupled in antiparallel alignment. Well defined ferroelectric transitions below the Fe(2+) orbital ordering temperature Too = 8.5 K are demonstrated. The ferroelectric polarization has two components. One component arises mainly from the noncollinear conical spin order associated with the spin-orbit coupling, which is thus magnetic field sensitive. The other is probably attributed to the Jahn-Teller distortion induced lattice symmetry breaking, occurring below the orbital ordering of Fe(2+). Furthermore, the coupled ferroelectric polarization and magnetization in response to magnetic field are observed. The present work suggests that spinel FeCr2S4 is a multiferroic offering both ferroelectricity and ferrimagnetism with large net magnetization.
多铁性的核心问题之一是铁电极化与磁化的强耦合，而到目前为止，大多数多铁材料都具有反铁磁序，几乎没有磁化强度。具有亚铁磁序的磁性尖晶石化合物可能是替代的候选者，当同时激活铁电性时，它们可以提供大的磁化强度。在这项工作中，我们研究了尖晶石 FeCr2S4 的铁电性和磁性，其中 Fe(2+)亚晶格和 Cr(3+)亚晶格呈反平行排列耦合。在 Fe(2+)轨道有序温度 Too = 8.5 K 以下证明了明确的铁电转变。铁电极化有两个分量。一个分量主要来自于与自旋轨道耦合相关的非共线锥形自旋有序，因此对磁场敏感。另一个可能归因于 Jahn-Teller 畸变诱导的晶格对称性破坏，发生在 Fe(2+)的轨道有序之下。此外，观察到了铁电极化和磁化对磁场的耦合响应。本工作表明，尖晶石 FeCr2S4 是一种多铁材料，具有铁电性和亚铁磁性，具有大的净磁化强度。
