Fe⁵⁷ Mössbauer Effect and Magnetic Susceptibility of Hexavalent Iron Compounds; K₂FeO₄, SrFeO₄ and BaFeO₄

Pure samples of three hexavalent iron compounds, K 2 FeO 4 , SrFeO 4 and BaFeO 4 , were prepared and measurements of magnetic susceptibility and Fe 57 Mössbauer effect were carried out down to 2°K. Those were antiferromagnetic at low temperature and the Néel temperatures of K 2 FeO 4 and BaFeO 4 were about 5°K and 10°K respectively. The internal magnetic field extrapolated to 0°K was 140 kOe for K 2 FeO 4 and 130 kOe for BaFeO 4 . Because the Néel temperature of SrFeO 4 was below 2°K, the internal field was estimated from the spectrum in the presence of an external field (50 kOe). The obtained value was also about 140 kOe and the sign was found to be negative.