Rathore Satyapal Singh, Vitta Satish
Indian Institute of Technology Bombay, Mumbai 400076, India.
Sci Rep. 2015 May 19;5:9751. doi: 10.1038/srep09751.
(Ba/Sr)3NbFe3Si2O14 is a magneto-electric multiferroic with an incommensurate antiferromagnetic spiral magnetic structure which induces electric polarization at 26 K. Structural studies show that both the compounds have similar crystal structure down to 6 K. They exhibit a transition, TN at 26 K and 25 K respectively, as indicated by heat capacity and magnetization, into an antiferromagnetic state. Although Ba and Sr are isovalent, they exhibit very different static and dynamic magnetic behaviors. The Ba-compound exhibits a glassy behavior with critical slowing dynamics with a freezing temperature of ~35 K and a critical exponent of 3.9, a value close to the 3-D Ising model above TN, in addition to the invariant transition into an antiferromagnetic state. The Sr-compound however does not exhibit any dispersive behavior except for the invariant transition at TN. The dielectric constant reflects magnetic behavior of the two compounds: the Ba-compound has two distinct dispersive peaks while the Sr-compound has a single dispersive peak. Thus the compounds exhibit coupled 'multiglass' behavior. The difference in magnetic properties between the two compounds is found to be due to modifications to super exchange path angle and length as well as anti-site defects which stabilize either ferromagnetic or antiferromagnetic interactions.
(Ba/Sr)3NbFe3Si2O14是一种磁电多铁性材料，具有非公度反铁磁螺旋磁结构，在26 K时会诱导出极化。结构研究表明，这两种化合物在低至6 K时具有相似的晶体结构。如热容和磁化强度所示，它们分别在26 K和25 K时发生转变（TN），进入反铁磁状态。尽管Ba和Sr是等价的，但它们表现出非常不同的静态和动态磁行为。除了向反铁磁状态的不变转变外，Ba化合物还表现出具有临界慢化动力学的玻璃态行为，冻结温度约为35 K，临界指数为3.9，该值接近高于TN的三维伊辛模型。然而，Sr化合物除了在TN处的不变转变外，没有表现出任何色散行为。介电常数反映了这两种化合物的磁行为：Ba化合物有两个明显的色散峰，而Sr化合物有一个单一的色散峰。因此，这些化合物表现出耦合的“多玻璃”行为。发现这两种化合物之间磁性能的差异是由于超交换路径角度和长度的改变以及稳定铁磁或反铁磁相互作用的反位缺陷。
