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Structure and Magnetic Properties of the α‑NaFeO2‑Type Honeycomb Compound Na3Ni2BiO6

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posted on 02.12.2013, 00:00 by Elizabeth M. Seibel, J. H. Roudebush, Hui Wu, Qingzhen Huang, Mazhar N. Ali, Huiwen Ji, R. J. Cava
We present the structure and magnetic properties of Na3Ni2BiO6, which is an ordered variant of the α-NaFeO2 structure type. This layered compound has a 2:1 ordering of (Ni2+/Bi5+)­O6 octahedra within the a-b plane and sodium in octahedra between the layers. The structure is presented in the space group C2/m, determined through a combination of single crystal X-ray, powder neutron, and powder X-ray diffraction. Temperature dependent magnetic susceptibility measurements show Na3Ni2BiO6 to display long-range antiferromagnetic ordering below 11 K, despite the dominance of ferromagnetic interactions above TN as indicated by a positive Weiss constant. Heat capacity measurements and low-temperature neutron diffraction support the magnetic ordering and are consistent with a TN of 10.4 K. A magnetic phase can be refined with (010) antiferromagnetic ordering along the b-axis in the honeycomb layer and moments aligned parallel to c. The compounds Na3Mg2BiO6 and Na3Zn2BiO6, synthesized as nonmagnetic analogues of Na3Ni2BiO6, are briefly described.