MAGNETIC-PROPERTIES OF PARTIALLY-INVERTED ZINC FERRITE AEROGEL POWDERS

Fine powders of ZnFe2O4 with an average particle size of 10 nm and inv ersion parameter of 0.21 were synthesized by the aerogel procedure. Po rtions of the powders were calcined in air at 500 and 800 degrees C an d other portions were ball-milled for 10 h. The materials were charact erized by x-ray diffractometry, vibrating sample, and SQUID magnetomet ry, Mossbauer spectrometry, and low temperature calorimetry. Upon calc ination the powders underwent significant changes in grain size, inver sion parameter; and hence magnetic properties. The magnetic state of t he as-produced and calcined samples is best described as disordered an d highly dependent on temperature. Upon ball-milling the grain size va ried widely and the inversion parameter attained a value of 0.55. The magnetic properties of the ball-milled sample are similar to those of ferrimagnetic MgFe2O4 powders having comparable grain size and inversi on parameters. (C) 1997 American Institute of Physics.