CATIONIC DISTRIBUTION IN DEFECT CO-MN FERRITES FROM NEUTRON-DIFFRACTION

Submicron stoichiometric cobalt manganese ferrites oxidized in air, at low temperature (<500 degrees C) give defect spinel ferrites which ex hibit a substantial increase in coercivity, reaching a maximum for fer rites oxidized near 350 degrees C and slowly cooled (5 degrees C/min) from the oxidation temperature. Two Co(0.936)Mn(0.355)Fe(1.665)rectang le(0.044)O(4) Samples oxidized at 350 degrees 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 str uctural and magnetic parameters, indicating that the difference betwee n the coercivities has a purely local origin. Similar cationic distrib utions have been inferred Neutron diffraction reveals a classical coll inear ferrimagnetism on the A and B sublattices of the spinel structur e.