Magnetic properties of lithium zinc ferrite

The magnetization of Li-Zn ferrite, Li0.5−x/2ZnxFe2.5−x/2O4, with x = 0 to x = 1.0 Zn at./f.u. has been examined over the temperature range 4–950 K and for fields up to 90 kOe. Magnetization M and high-field incremental susceptibility χinc were compared with a calculation based on a localized canting model. A qualitative fit was found for M versus x for an exchange ratio JAB/JBB = 3–4, but the experimental and theoretical χinc versus x results were completely different. On the other hand, a good correlation was found between χinc and the probability of a B-site Fe having only one A-site Fe neighbor. The data also reveal low-temperature maxima in M in the 30–80 K range for x = 0.4 up to 1.0; the effect is most pronounced for x = 0.7. Weak mictomagnetic behavior is found for x = 0.5 and 0.6. Samples with x = 0.9 and 1.0 show no spontaneous moment down to 4 K, but exhibit initial susceptibility maxima at about 15 K with extrapolated Curie temperatures of 10 K and 4 K, respectively. For x = 0.8, a Curie temperature of 238 K is obtained. These are considerably lower than literature values.