Synthesis and characterization of the crystal structure and magnetic properties of the new fluorophosphate LiNaCo[PO4]F

The new compound LiNaCo[PO4]F was synthesized by a solid state reaction route, and its crystal structure was determined by single-crystal X-ray diffraction measurements. The magnetic properties of LiNaCo[PO4]F were characterized by magnetic susceptibility, specific heat, and neutron powder diffraction measurements and also by density functional calculations. LiNaCo[PO4]F crystallizes with orthorhombic symmetry, space group Pnma, with a = 10.9334(6), b = 6.2934(11), c = 11.3556(10) angstrom, and Z = 8. The structure consists of edge-sharing CoO4F2 octahedra forming CoFO3 chains running along the b axis. These chains are interlinked by PO4 tetrahedra forming a three-dimensional framework with the tunnels and the cavities filled by the well-ordered sodium and lithium atoms, respectively. The magnetic susceptibility follows the Curie Weiss behavior above 60 K with theta = -21 K. The specific heat and magnetization measurements show that LiNaCo[PO4]F undergoes a three-dimensional magnetic ordering at T-mag = 10.2(5) K. The neutron powder diffraction measurements at 3 K show that the spins in each CoFO3 chain along the b-direction are ferromagnetically coupled, while these FM chains are antiferromagnetically coupled along the a-direction but have a noncollinear arrangement along the c-direction. The noncollinear spin arrangement implies the presence of spin conflict along the c-direction. The observed magnetic structures are well explained by the spin exchange constants determined from density functional calculations. © 2012, American Chemical Society.

Keywords

Spin, Cathodes, Lithium, Antiferromagnetism, X-ray diffraction, Neutrons, Valence, Metals

Citation

Ben Yahia, H., Shikano, M., Koike, S., Tatsumi, K., Kobayashi, H., Kawaji, H., Avdeev, M., Miiller, W., Ling, C. D., Liu, J., & Whangbo, M. H. (2012). Synthesis and characterization of the crystal structure and magnetic properties of the new fluorophosphate LiNaCo[PO4]F. Inorganic Chemistry, 51(16), 8729-8738. doi:10.1021/ic300374w