The structural stability and electrical properties of Sr2FeMoO6 under high pressure at room temperature have been studied using energy dispersive x-ray diffraction with synchrotron radiation and resistance and capacitance measurements. The x-ray diffraction results show that the structure of Sr2FeMoO6 remains stable up to 40 GPa. The equation of state of Sr2FeMoO6 is obtained from the V/V0–P relationship. The bulk modulus B0 and its first-order derivative B0′ of Sr2FeMoO6 were calculated based on the Birch–Murnaghan equation. The electrical resistance undergoes a metallic transition at about 2.1 GPa. The metallic transition may be caused by a change in the electronic structure induced by high pressure.

The crystal structures and Mössbauer spectra of various mixed oxides LaFe1−xMnxO3 and LaFe1−xCoxO3 (x = 0 to 0.9) are determined and measured at room temperature. The results indicate that the crystal structure of both the La–Fe–Mn–O and the La–Fe–Co–O systems vary with the relative content of manganese and cobalt in the compounds. Mössbauer parameters of the 57Fe nucleus in these compounds, such as isomer shift, electric quadrupole splitting, linewidth, and internal magnetic field, are obtained from the experimental spectra. Various possible substitutions of Mn and Co ions for Fe ions in the lattice and the effect of the Mn and Co ions on the Mössbauer spectra of the 57Fe nucleus in these compounds are discussed. Both manganese and cobalt ions in these compounds are mainly in a low spin state. The change in the crystal structure is in accordance with the change in the magnetic behaviour of these compounds.

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