Spin-wave spectrum for barium ferrite (abstract)

Abstract

In order to determine whether barium ferrite will be suitable for microwave and millimeter wave device applications, it is essential to calculate the intrinsic ferrimagnetic resonance linewidth for perfect single crystals of this compound. The two mechanisms believed to be responsible for the intrinsic linewidth of barium ferrite, the Kasuya–LeCraw1 two-magnon one-phonon process and the two-magnon scattering caused by the time fluctuations of 2b site (trigonal symmetry site) ions,2 require knowledge of the magnon dispersion relations throughout the Brillouin zone, and not just near the zone center. We describe the calculations of the spin-wave spectrum for barium ferrite, which is a highly complex exchange-coupled hexagonal ferrimagnetic compound, using a method similar to that used by Harris for YIG.3 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 cm4.