Investigation of magnetic frustration in A₂FeMO₆(A Ca, Sr, Ba; M Nb, Ta, Sb) by magnetometry and Mössbauer spectroscopy

Perovskite-related compounds in the series A2FeMO6(A Ca, Sr, Ba; M Nb, Ta, Sb) have been prepared using the standard techniques of solid state chemistry and characterized by X-ray powder diffraction, magnetometry and Mössbauer spectroscopy. All but the 6H hexagonal compound Ba2FeSbO6 adopt cubic or pseudo-cubic crystal structures and show a magnetic susceptibility maximum at ca. 25 K. Field cooled and zero-field cooled susceptibility data show a hysteresis below this maximum. The Mössbauer spectra recorded at 4.2 K comprise a single magnetic hyperfine pattern typical of Fe3+, but with a high degree of line broadening. The spectra show a relaxational (nonBrillouin) collapse above 20 K. The data are described in terms of spin-glass behaviour and the factors controlling the magnetic properties are discussed.