Magnetic Ordering and Structural Transition in the Ordered Double-Perovskite Pb2NiMoO6
Magnetic Ordering and Structural Transition in the Ordered Double-Perovskite Pb2NiMoO6
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DOI：
10.1021/acs.chemmater.1c02826
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发表时间：
2021-12
影响因子：
8.6
通讯作者：
Jianfa Zhao;Xiao Wang;X. Shen;C. Sahle;Cheng Dong;H. Hojo;Y. Sakai;Jun Zhang;Wenmin Li;Lei Duan;T. Chan;C. Chen;Johannes Falke;Cheng-En Liu;C. Kuo;Z. Deng;Xiancheng Wang;R. Yu;R. Yu;Zhiwei Hu;M. Greenblatt;C. Jin
中科院分区：
文献类型：
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作者：
Jianfa Zhao;Xiao Wang;X. Shen;C. Sahle;Cheng Dong;H. Hojo;Y. Sakai;Jun Zhang;Wenmin Li;Lei Duan;T. Chan;C. Chen;Johannes Falke;Cheng-En Liu;C. Kuo;Z. Deng;Xiancheng Wang;R. Yu;R. Yu;Zhiwei Hu;M. Greenblatt;C. Jin
在高温高压条件下制备了B位有序双钙钛矿结构的Pb2NiMoO6。同步辐射粉末X射线衍射数据的结构分析表明，Pb2NiMoO6为单斜晶系，空间群为Pc(NO.7)，其中Ni和Mo离子以岩盐型有序排列。磁学和比热分析表明，Pb2NiMoO6在18K和26K发生了反铁磁(AFM)两步相变。Ni-L2，3边和Mo-L3边的X射线吸收光谱和铅-L3边的高分辨部分荧光产额表明Pb2+2Ni2+Mo6+O6价态。虽然在A2NiMoO6(A=Sr2+，Pb2+和Ba2+)中，A离子的尺寸从Sr2+(1.44°)到Pb2+(1.49°)再到Ba2+(1.61°)逐渐增大，但Pb2NiMoO6的对称性结构和原子力显微镜转变温度Tn比Sr2NiMoO6(I4/m，Tn=81K)和Ba2NiMoO6(Fm3̅m，Tn=K)低得多，这是由于Pb2+的单对电子效应导致NiO6和MoO6八面体的大变形所致。此外，在Pb2NiMoO6中还观察到了从高温中心对称的立方̅相到低温非中心对称的单斜相Pc的对称性破缺相变。
The B-site-ordered double-perovskite Pb2NiMoO6was prepared at high pressure and high temperature. The structural analysis of synchrotron powder X-ray diffraction data shows that Pb2NiMoO6crystallizes into monoclinic symmetry with the space groupPc(no. 7), where the Ni and Mo ions are ordered in a rock-salt-type manner. The magnetic and specific heat characterizations reveal unusual two-step antiferromagnetic (AFM) transitions at 18 and 26 K for Pb2NiMoO6. The X-ray absorption spectra at the Ni-L2,3edge and the Mo-L3edge and the high-resolution partial fluorescence yield at the Pb-L3edge indicate Pb2+2Ni2+Mo6+O6valence states. Although in A2NiMoO6(A = Sr2+, Pb2+, and Ba2+), the size of the A cation increases gradually from Sr2+(1.44 Å) to Pb2+(1.49 Å) to Ba2+(1.61 Å), Pb2NiMoO6exhibits much lower symmetry structure and AFM transition temperature,TN, compared with Sr2NiMoO6(I4/m,TN= 81 K) and Ba2NiMoO6(Fm3̅m,TN= 64 K), which is attributed to the large distortion of NiO6and MoO6octahedra induced by the lone pair electron effect of Pb2+with a 6s2electronic configuration. Moreover, symmetry-breaking phase transition from a high-temperature centrosymmetric, cubicFm3̅mphase to a low-temperature non-centrosymmetric, monoclinicPcphase was observed at 393–413 K in Pb2NiMoO6.