EFFECT OF CATION ARRANGEMENT ON THE MAGNETIC-PROPERTIES OF LITHIUM FERRITES (LIFEO2) PREPARED BY HYDROTHERMAL REACTION AND POSTANNEALING METHOD

The magnetic properties of several LiFeO2 polymorphs (different cation arrangements in a cubic close-packed oxygen structure) have been exam ined by magnetic susceptibility measurements and Mossbauer spectroscop y. Samples with relatively low ferromagnetic impurity levels have been obtained by hydrothermal reaction of FeCl3 . 6H(2)O or FeOOH with LiO H . H2O and subsequent annealing in air, alpha-NaFeO2 with no detectab le ferromagnetic impurity has been obtained by hydrothermal reaction o f alpha-FeOOH and NaOH. While alpha-NaFeO2 revealed only one anomaly a t 11 K (Neel point) in the magnetic susceptibility-temperature curves, each LiFeO2 sample shows two anomalies (40-50 and 90-280 K). Mossbaue r data confirm that iron is present in the high-spin 3+ state accordin g to the values of the internal field at 4.2 K and isomer shifts at 30 0 K. The relationship between the cation arrangements and the Neel tem perature is discussed for LiFeO2. (C) 1998 Academic Press.