Cationic Distribution in Defect Co-Mn Ferrites from Neutron Diffraction

Submicron stoichiometric cobalt manganese ferrites oxidized in air, at low temperature (<500°C) give defect spinel ferrites which exhibit a substantial increase in coercivity, reaching a maximum for ferrites oxidized near 350°C and slowly cooled (5°C/min) from the oxidation temperature. Two [MATH] samples oxidized at 350°C but exhibiting notably different coercivities because of different cooling rates (Hc=1750 Oe after quenching ; Hc=2350 Oe after slow cooling) have been analyzed by neutron diffraction at T=6K. They exhibit almost exactly the same structural and magnetic parameters, indicating that the difference between the coercivities has a purely local origin. Similar cationic distributions have been inferred. Neutron diffraction reveals a classical collinear ferrimagnetism on the A and B sublattices of the spinel structure