Displacive structural phase transitions and the magnetic ground state of quadruple perovskite YMn7O12
Displacive structural phase transitions and the magnetic ground state of quadruple perovskite
YMn7O12
复制标题
四重钙钛矿YMn7O12的位移结构相变和磁基态
作者：
R. Johnson;D. Khalyavin;P. Manuel;Y. Katsuya;Masashi Tanaka;Y. Matsushita;Lei Zhang;K. Yamaura;A. Belik
我们提出了一个实验研究的结构和磁性相变的四重钙钛矿YMn 7 O 12。当温度低于640 K时，在长程B位Mn 3+轨道序的驱动下，发生位移结构相变，使晶体对称性从立方（Im <$3）降低到单斜（I 2 /m）。第二，非常规的结构相变发生在进一步冷却低于200 K，其特征在于静态原子位移（P 2 1 /n）以及偶极玻璃状状态的钇。这种低温结构转变是由钇的欠键合驱动的，钇的欠键合是由于主要容纳A位点锰离子的四重钙钛矿所特有的八面体倾斜的刚性框架而存在的。基态亚铁磁结构也被确定，类似于在其他R Mn 7 O 12化合物中发现的，不存在低温结构相变。
We present an experimental study of the structural and magnetic phase transitions of the quadruple perovskite YMn 7 O 12 . On cooling below 640 K a displacive structural phase transition occurs, lowering the crystal symmetry from cubic ( Im ¯3) to monoclinic ( I 2 /m ), driven by long range B site Mn 3+ orbital order. A second, unconventional structural phase transition takes place on further cooling below 200 K, which is characterised by static atomic displacements ( P 2 1 /n ) as well as a dipolar-glass-like state of yttrium. This low temperature structural transition is driven by the underbonding of yttrium, which is present due to the rigid framework of octahedra tilts unique to the quadruple perovskites that primarily accommodates A site manganese ions. A ground state ferrimagnetic structure was also determined, similar to that found in other R Mn 7 O 12 compounds that do not present a low temperature structural phase transition.