Exchange frequency resonance consider a Ferrimagnet with two sub-lattices A and B of magnetizations M_A, and M_B, where M_B, is opposite to M_A when the spin system is at rest. The gyro magnetic ratios are γ_A, γ_B, and the molecular fields are BA = – λM_B; B_B = – λM_A. Show that there is a resonance at w²₀ = λ² (γ_A|M_B| - γ_B|M_A|² this is called the exchange frequency resonance.