A Neutron Diffraction, Magnetic Susceptibility, and Mössbauer-effect Study of the (MnₓFe₁₋ₓ)yO Solid Solutions


A total of 14 mixed-metal oxides, (MnxFe1-x)yO, with x ranging from zero to 0.975 and y ranging from 0.910 to 0.998, have been prepared. Chemical analysis and powder neutron diffraction studies confirm that nonstoichiometry in these oxides is accommodated by the formation of defect clusters similar to those observed in FeyO. Magnetic susceptibility measurements from 50 to 300 K indicate that the Néel temperature decreases approximately linearly from ca. 200 K for FeyO to 142 K for (Mn0.66Fe0.34)0.954O. The room-temperature Mössbauer-effect spectra show the expected amount of high-spin iron(III) with isomer shifts in the range of 0.45 to 0.24 mm/s, decreasing with increasing manganese content. The high-spin iron(II) absorption in FeyO may be fitted with two quadrupole doublets with isomer shifts of ca. 1.00 and 0.95 mm/s and quadrupole interactions of ca. 0.42 and 0.80 mm/s respectively. The major new feature apparent upon the addition of manganese is a third quadrupole doublet with an isomer shift of ca. 1.05 mm/s and splittings in the range of 0.96 to 1.38 mm/s. The area-weighted average quadrupole interaction, which is ca. 0.6 mm/s for FeyO, increases slowly with increasing manganese content to a maximum of ca. 0.7 mm/s at 50% manganese. At higher levels of manganese, the area-weighted average quadrupole interaction drops sharply to a value of ca. 0.1 mm/s at 97.5% manganese. This behavior may be understood in terms of the number of defects present and the nature and distribution of the iron/manganese near-neighbor ions. The iron(II) isomer shift increases slightly from 0.95 to 1.10 mm/s with increasing manganese content. © 1982 American Chemical Society.



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© 1982 American Chemical Society (ACS), All rights reserved.

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01 Jan 1982