P. Lubitz et al., EFFECTS OF ANNEALING ON THE MICROWAVE PROPERTIES OF SPIN-SPRAY NI-ZN FERRITES, IEEE transactions on magnetics, 30(6), 1994, pp. 4539-4541
We have studied the properties of a series of spinel ferrite thin film
s prepared from aqueous solutions at temperatures slightly below 100 d
egrees C, for a range of compositions from pure Fe3O4 to about Ni.34Zn
.18Fe2.48O4. As made, the films are semiconducting and have high diele
ctric losses, but have narrow ferromagnetic resonance linewidths and o
ften display standing spinwave spectra. As a result of annealing in ai
r at temperatures above 300 degrees C, these ferrites undergo a transf
ormation to a State having much higher resistivity and a reduced magne
tic moment compared to as-grown films. This annealing decreases the mi
crowave dielectric losses. but increases the ferromagnetic resonance l
inewidth. The changes in these properties with annealing are consisten
t with a partial transformation from spinel to maghemite, gamma-Fe2O3.