Magnetic properties and structural transitions of orthorhombic fluorite-related compounds Ln3MO7 (Ln=rare earths, M=transition metals)
Magnetic properties and structural transitions of orthorhombic fluorite-related compounds Ln3MO7 (Ln=rare earths, M=transition metals)
复制标题
DOI：
10.1016/j.jssc.2010.09.005
复制
发表时间：
2010-11
影响因子：
3.3
通讯作者：
M. Wakeshima;Y. Hinatsu
中科院分区：
文献类型：
--
作者：
M. Wakeshima;Y. Hinatsu
研究了三元稀土过渡金属氧化物Ln3Mo7(Ln=稀土，M=过渡金属)的磁性和结构转变。在本研究中，我们制备了一系列钼酸盐Ln_3MoO_7(Ln=La-Gd)。它们在立方萤石的正交超结构中结晶，空间群为P212121，其中Ln3+离子占据两个不同的晶位(8配位和7配位)。在370-710K温度范围内，所有化合物都表现出从空间群P212121到Pnma的相变。通过测量1.8~400K的磁化率和0.4~400K的比热，表征了它们的磁性能。Gd3MoO7在1.9K出现反铁磁相变。Sm_3MoO_7的比热测量和磁性比热分析表明，由于Sm磁矩在不同晶位的有序化，在2.5K发生了7配位的Sm离子的反铁磁有序，在0.8K发生了8配位的Sm离子的有序化，这是一个“两步”的反铁磁转变。将Ln3MoO7的结果与Ln3Mo7(M=Nb、Ru、Sb、Ta、Re、Os或Ir)的磁性和结构转变进行了比较。
Magnetic properties and structural transitions of ternary rare-earth transition-metal oxides Ln3MO7(Ln=rare earths, M=transition metals) were investigated. In this study, we prepared a series of molybdates Ln3MoO7(Ln=La–Gd). They crystallize in an orthorhombic superstructure of cubic fluorite with space group P212121, in which Ln3+ions occupy two different crystallographic sites (the 8-coordinated and 7-coordinated sites). All of these compounds show a phase transition from the space group P212121to Pnma in the temperature range between 370 and 710K. Their magnetic properties were characterized by magnetic susceptibility measurements from 1.8 to 400K and specific heat measurements from 0.4 to 400K. Gd3MoO7shows an antiferromagnetic transition at 1.9K. Measurements of the specific heat for Sm3MoO7and the analysis of the magnetic specific heat indicate a “two-step” antiferromagnetic transition due to the ordering of Sm magnetic moments in different crystallographic sites, i.e., with decreasing temperature, the antiferromagnetic ordering of the 7-coordinated Sm ions occur at 2.5K, and then the 8-coordinated Sm ions order at 0.8K. The results of Ln3MoO7were compared with the magnetic properties and structural transitions of Ln3MO7(M=Nb, Ru, Sb, Ta, Re, Os, or Ir).