Dependence of the Ferromagnetic Resonance Line Width on the Shape of the Specimen

The dependence of line width of the ferromagnetic resonance on the shape of the sample is examined on phenomenological grounds. If a damping term of the Bloch-Bloembergen type is assumed in the equation of motion of the magnetization, the line width for an ellipsoidal sample is given by ΔH=[1+Ms2γ2(Nx−Ny)2/4ω2]−122/γT2. The Landau-Lifshitz form of damping leads to a line width which is independent of the shape of the specimen.