Synthesis, crystal structure and magnetic properties of β-Na3FeO3

β-Na3FeO3 was prepared via the azide/nitrate route. Stoichiometric mixtures of the precursors (Fe2O3, NaN3 and NaNO3) were heated in a special regime up to 450 °C and annealed at this temperature for 50 h in specially designed silver containers. Single crystals have been grown by subsequent annealing of the reaction product at 500 °C for 1000 h, in silver crucibles which were sealed in glass ampoules under dried Ar. According to the X-ray analysis of the crystal structure (I  a, Z=8Z=8, a=6.1408(4)a=6.1408(4), b=10.6944(7)b=10.6944(7), c=11.7920(8) Åc=11.7920(8) Å, β=90.653(3)°β=90.653(3)°, 1667 independent reflections, R1=3.37%R1=3.37% (Fo>4σ(Fo)Fo>4σ(Fo)) chains of corner-sharing FeO4 tetrahedra are the main structural feature. With this respect, there is full correspondence to the structure of former α-Na3FeO3. The most prominent difference between the α- and β-form can be noted in the periodicity and the mutual arrangement of the 1∞FeO3 polyanions. The magnetic susceptibility provides evidence for a strong antiferromagnetic exchange between Fe+3 ions. The best fit of the susceptibility data yields an average value of the coupling strength between magnetic centres within the FeO3 chains of J/kB=−62 KJ/kB=−62 K (−43 cm−1).

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