Belik Alexei A
Research Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS), Namiki 1-1, Tsukuba 305-0044, Ibaraki, Japan.
Molecules. 2025 Apr 14;30(8):1749. doi: 10.3390/molecules30081749.
A site-ordered quadruple perovskites, AA'BO, can have 3 transition metals at A' and B sites, and show complex magnetic interactions and behavior. Additional complexity appears when B site-ordered arrangements are realized in AA'BB'O. In this work, A site-ordered quadruple perovskites, RMnNiMnO with R = Bi, Ce, and Ho, were prepared by a high-pressure, high-temperature method at about 6 GPa and about 1500 K. The R = Bi and Ce samples were found to crystallize in space group -3 with a disordered distribution of Ni and Mn cations in one B site. On the other hand, the R = Ho sample crystallized in space group -3 and showed partial ordering of Ni and Mn cations between two B sites. The structural data (and bond valence sums) suggest that cerium has the oxidation state +3, which is unusual for such perovskites. Magnetic properties were investigated by magnetic susceptibility and specific heat measurements, which showed the presence of one magnetic transition near 36 K for R = Bi; there was evidence for the presence of two magnetic transitions near 27 K and 33 K for R = Ce, and near 10 K and 36 K for R = Ho. Curie-Weiss parameters were estimated for all samples from high-temperature magnetic measurements up to 750 K. The total effective magnetic moment for R = Ce also suggests the presence of Ce. A magnetic field of 90 kOe had the largest effect on the specific heat of the R = Ho sample, and almost no effects on the specific heat of the R = Bi sample.
一种具有位点有序的四重钙钛矿结构AA'BO，在A'和B位点可以有3种过渡金属，并表现出复杂的磁相互作用和行为。当在AA'BB'O中实现B位点有序排列时，会出现额外的复杂性。在这项工作中，通过在约6 GPa和约1500 K的高压高温方法制备了具有位点有序的四重钙钛矿结构RMnNiMnO，其中R = Bi、Ce和Ho。发现R = Bi和Ce的样品结晶于空间群-3，在一个B位点中Ni和Mn阳离子呈无序分布。另一方面，R = Ho的样品结晶于空间群-3，并且在两个B位点之间显示出Ni和Mn阳离子的部分有序排列。结构数据（和键价和）表明铈具有+3氧化态，这对于此类钙钛矿来说是不寻常的。通过磁化率和比热测量研究了磁性能，结果表明对于R = Bi，在36 K附近存在一个磁转变；有证据表明对于R = Ce，在27 K和33 K附近存在两个磁转变，对于R = Ho，在10 K和36 K附近存在两个磁转变。通过高达750 K的高温磁测量对所有样品估算了居里-外斯参数。R = Ce的总有效磁矩也表明存在Ce。90 kOe的磁场对R = Ho样品的比热影响最大，而对R = Bi样品的比热几乎没有影响。
