Renormalized resonance frequencies of a ferrite sphere coupled to an LR circuit: Comparison of theory and experiment

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. © 2005 Wiley Periodicals, Inc. Concepts Magn Reson Part B (Magn Reson Engineering) 24B: 39–45, 2005