Charge disproportionation and ordering in La1/3Sr2/3FeO3-δ

The perovskite La1/3Sr2/3 FeO3-delta was investigated by neutron diffraction, magnetic and Mossbauer spectroscopy measurements. La1/3Sr2/3FeO3-delta undergoes magnetic ordering at T = 190-200 K accompanied by charge disproportionation. Magnetic peaks due to charge ordering are observed below 200 K. The charge ordering is gradually developed below 200 K along with a charge disproportionation, 2Fe(4+) double right arrow Fe3+ + Fe5+. La1/3Sr2/3FeO3-delta shows an antiferromagnetic structure at low temperature. Magnetic moments of about 3 and 1.3 mu(B) were obtained from the neutron diffraction data refinement for Fe3+ and Fe5+ at 15 K, respectively, which suggest that both Fe ions are in a low spin state. These values are significantly lower than those reported by Battle et al for La1/3Sr2/3FeO2.98. Mossbauer spectra indicate that full charge ordering might be reached below 20 K with no Fe4+.