The resonance frequencies of a system containing two or four magnetic sublattices with different gyro-magnetic ratios are calculated. It is found that in many cases the results reduce to the standard formulas of ferromagnetic and antiferromagnetic resonance; they are stated, however, in terms of an effective gyromagnetic ratio equal to the quotient of the net magnetic moment and the net angular momentum of the system. Line splitting due to the existence of several normal modes of nearly equal frequencies, and the effect of the sublattice structure upon the anisotropy contribution to the line width are also discussed. The calculated values of effective $g$ values and line widths as a function of composition are compared with the experimental results for the nickel ferrite-aluminates.

• Received 28 May 1953

DOI:https://doi.org/10.1103/PhysRev.91.1085