Physical properties of the novel Jarosite-type compound NaFe3(SeO4)2(OH)6

A selenate analogue of sodium Jarosite NaFe3(SeO4)2(OH)6 has been synthesized by precipitation from aqueous solution. We have newly determined the structural parameters by powder X-ray diffraction refinement. The structure is similar to that of sulfate Jarosite analogues, while the unit cell volume is larger. The temperature dependence of the magnetic susceptibility shows a cusp-like anomaly at 45 K, and the spontaneous magnetization appears below 33 K. We have measured the Mössbauer spectra of 57Fe3+(S=2/5) ions, and revealed an anomalous fluctuation of the hyperfine field.