Published online by Cambridge University Press: 21 February 2011
Using rf-sputtering techniques, the end member of the BixY3-xFe5O12 family, Bi3Fe5O12 (BiIG) has been grown. The Bi3Fe5O15 films exhibit a large maximum Farady rotation of −2.7 × 105 deg/cm at 550 nm and it is largerthan 105 deg/cm in the range of 520 nm to 630 nm. The Curie temperatures, the temperature dependence of the magnetization, the coercivity, the internal fields, ferromagnetic resonance linewidth and the optical absorption spectra have been measure. In the high Bi concentration films, the Hansen form of the molecular field equations in which the molecular field coefficients were modified to account for the observed increase in the Curie temperature were found to be inadequate to evaluate the temperature dependence of the magnetization. In addition to those terms, a third sublattice is required to fit the data with some of the moment at the tetrahedral iron sublattice being transferred to that of the Bi sublattice. Reasonable agreement between the molecular field model and the data are obtained if the spin on the tetrahedral iron lattice is decreased by 0. 50μB and the Bi ion moment increased to 0. 25% decrease in the absorption gap is also observed in the BiIG.