Magnetic Susceptibilities and M?ssbauer Spectra of Perovskites A2FeNbO6 (A=Sr, Ba)

Perovskite-type compounds A2FeNbO6 (A=Sr, Ba) were prepared. Their powder X-ray diffraction measurements and the Rietveld analysis show that the cations Fe3+ and Nb5+ over the six-coordinate sites of the perovskite structure are arranged randomly for Sr2FeNbO6 and some of them order regularly for Ba2FeNbO6. They show magnetic susceptibility maxima at ca. 25 K. Below the temperatures, the divergence of the magnetic susceptibilities measured between the zero-field-cooled condition and the field-cooled condition has been measured. Field-cooled and zero-field-cooled susceptibilities show a hysteresis below maximum temperatures. These results indicate the existence of a ferromagnetic component in the magnetic moment. M?ssbauer spectra measured at 6 K comprise a single magnetic hyperfine pattern typical of Fe3+, but with a high degree of line broadening. These data are discussed in terms of antiferromagnetic interactions with a ferromagnetic component.