μ3-Na5Ba10Fe7O2(PO4)14: A triangular magnetic lattice

There has been an extensive interest in cryst. solids contg. magnetic nanostructures. The chem. systems that we have paid special attention to thus far in our lab. include transition-metal-contg. oxy compds., such as silicates, phosphates and arsenates. The oxy anions, like org. ligands, serve as closed-shell, nonmagnetic "chelating" agents that structurally isolate the transition-metal-oxide nanostructures. This provides electronic confinement for the study of spin-spin and spin-orbital interactions of fundamental and technol. importance. We have recently synthesized a new iron (III) phosphate compd. using high-temp. flux methods in molten salt media. The title compd., μ3-Na5Ba10Fe7O2(PO4)14, crystallizes in a trigonal space group, P-3m1 (no. 164). The X-ray single crystal structure reveals that the Fe3+ cations adopt FeOn coordination, including square pyramidal (n = 5) and octahedral (n = 6) geometries. Three FeO5 square pyramids share a corner oxide anion, μ3 oxo-, and, in turn, create magnetic equilateral triangles that are structurally confined from one another by the nonmagnetic oxyanion, (PO4)3-. The temp.-dependent magnetic measurements have revealed that this solid has a ferromagnetic anomaly at high temps. (Tc textgreater 300K). The subsequent field-dependent studies at temps. near Tc (T = 300K) have shown magnetic hysteresis. In this presentation, we will show the results of solid state synthesis, crystal growth, structure anal., UV-Vis spectroscopy, magnetic characterization and heat capacity measurements.