Howard Christopher J, Campbell Branton J, Stokes Harold T, Carpenter Michael A, Thomson Richard I
School of Engineering, University of Newcastle, Callaghan, NSW 2308, Australia.
Acta Crystallogr B Struct Sci Cryst Eng Mater. 2013 Dec;69(Pt 6):534-40. doi: 10.1107/S205251921302993X. Epub 2013 Nov 18.
The available data on the structural and magnetic transitions in multiferroic hexagonal YMnO3 have been reviewed, first making use of the computer programs from the group theoretical ISOTROPY software suite to list possible crystal and magnetic structures, then taking into account the capability of neutron diffraction and other physical methods to distinguish them. This leads to a clear view of the transformation sequence, as follows. Hexagonal YMnO3 is paraelectric in P63/mmc at elevated temperatures, and undergoes a single structural transition on cooling through 1250 K to a ferrielectric phase in P63cm that is retained through room temperature. At a much lower temperature, 70 K, there is a magnetic transition from paramagnetic to a triangular antiferromagnetic arrangement, most likely with symmetry P63'cm'. Comment is made on the unusual coupling of ferroelectric and magnetic domains reported to occur in this material, as well as on the so-called `giant magneto-elastic' effect.
本文综述了多铁性六角形YMnO₃中结构和磁转变的现有数据，首先利用群论ISOTROPY软件包中的计算机程序列出可能的晶体和磁结构，然后考虑中子衍射和其他物理方法区分它们的能力。这得出了如下清晰的转变序列。六角形YMnO₃在高温下于P63/mmc空间群中为顺电体，在冷却至1250 K时经历单次结构转变，转变为P63cm空间群中的铁电相，并在室温下保持。在低得多的温度70 K时，发生从顺磁到三角反铁磁排列的磁转变，最可能具有P63'cm'对称性。文中对该材料中报道的铁电和磁畴的异常耦合以及所谓的“巨磁弹性”效应进行了评论。
