In-field MÃ\x89¬ssbauer spectra for LaxSr1-xFeO3-y (x=1/3, 1/2) above their charge disproportionation temperature

The charge disproportionation (CD) was first observed by Mossbauer spectroscopy in the sample La_1/3Sr_2/3FeO₃, in which the Fe ions could take non-integral charge states between Fe³⁺ and Fe⁵⁺ depending on the composition. The results of external field Mossbauer spectroscopy for La_xSr_1-xFeO_3-y (x=1/3,1/2) concerning how the external magnetic field affects the CD state above their transition temperature were discussed. Chemical analysis showed that oxygen non-stoichiometry y were 0.04 and 0.025 for x=1/3 and 1/2, respectively. External magnetic field up to 6 T was applied both parallel and perpendicular to the direction of gamma-ray propagation using a split magnet superconductor cryostat. As the external magnetic field is parallel to the gamma-ray direction, the spectral lines 2 and 5 are suppressed (the lines 3 and 4 are overwhelmed by the strong central singlet). The magnetic moments are aligned perpendicular to the gamma-ray direction.