ABSTRACT:We derive a formula for the AC susceptibility of a ferrite spherical resonator coupled to an LR circuit by formulating the problem in terms of a feedback mechanism. This technique allows us to find an analytical expression for the dependence of the shift in resonance frequency on the loop-crystal coupling strength, the circuit parameters, and the saturation magnetization of the ferrite. Finally, we compare these predictions to experimental results on YIG and Ga:YIG spheres. This coupling provides a simple way of tuning the uniform mode frequency relative to the spin-wave spectrum.