MOSSBAUER STUDY OF PEROVSKITES OF COMPOSITION SRFE1-X CRXO3-Y

Single-phase specimens of composition SrFe1-xCr xO3-y with x≤0.75 were prepared by usual ceramic techniques. Specimens with x≥0.05 were found to have apparently cubic perovskite structure. The lattice constant of this system increases sharply to a broad maximum at x=0.30 with increasing chromium concentration. Mössbauer spectra for specimens with x=0.20 to 0.30, composed of two sets of six peaks at room temperature, show that these specimens are magnetically ordered at room temperature. The two sets of six peaks may be attributable to Fe3+ ions and Fe4+ ions, respectively. The spectrum of SrFe 0.5Cr0.5O3-y taken at room temperature, consists of two peaks split by electric quadrupole interaction, attributed to Fe3+. The values of isomer shift and quadrupole splitting are +0.16 mm/sec and 0.97 mm/sec, respectively. The effective Bohr magneton number obtained from the slope of reciprocal susceptibility curve vs temperature is approximately 4.0 μB, which is close to the value expected for 0.50 Fe3+, 0.25 Cr3+, and 0.25 Cr6+. Both SrFe0.75Cr0.25O3-y and SrFe 0.5Cr0.5O3-y are antiferromagnets with a small residual magnetization. It seems that the usual superexchange interaction cannot explain why the Néel temperature of SrFe0.75Cr 0.25O3-y is much higher than that of SrFeO3. Differences in the chemical bonding character may have to be considered. © 1969 The American Institute of Physics.