Localized spin canting in partially inverted ZnFe2O4 fine powders

Stoichiometric zinc ferrite fine powders showing long-range magnetic order to temperatures above 30 K have been prepared by the supercritical sol-gel method. The low-temperature magnetic behavior of the as-produced powder, and portions calcined at 500 and 800 degrees C, were determined by Mossbauer-effect measurements in an applied field of 7 T. The inversion parameter of the as-produced powder was 0.21, with those of the calcined powders being <0.05. A localized canted spin structure was found at 4.2 K, where spin canting was measured for both the Fe3+ moments aligned parallel and antiparallel to the applied field. The canting for antiparallel aligned spins vanished above the Neel temperature, where the fractional areas of the absorption peaks approached those expected from the inversion parameters. Spin canting persisted for the parallel moments to temperatures of 20-30 K, where the broadened sextets then showed collinear magnetic alignment. Slow relaxation processes were observed in Mossbauer spectra at 4.2 K, while the spectra was affected by the onset of fast relaxation processes at higher temperatures. The ability to adjust the inversion parameters in these powders make them excellent candidates for the study of long-range magnetic ordering in nearly antiferromagnetic spinel ferrites. [S0163-1829(99)10229-7].