Spin-wave spectrum for barium ferrite

We describe the calculation of the spin-wave spectrum for barium ferrite, a complex exchange-coupled hexagonal ferrimagnetic compound, using a method first used in a similar calculation for yttrium iron garnet (YIG). The exchange integrals are calculated by fitting the Weiss molecular field approximation to the sublattice magnetizations while including single-ion anisotropy. The value for the space-averaged stiffness constant as calculated from the acoustic mode of the spin-wave spectrum is 2.5×10−9 Oe cm2, which compares favorably with values obtained by domain wall resonance, considering the accuracy of such measurements.