Interpretation of Ferromagnetic Resonance Measurement Made in a Nonresonant System

The nonresonant shorted waveguide, NRS, method for measuring the ferromagnetic resonance line width, ΔH, is discussed. The major aim of the paper is to test the usual resonator formula for getting unloaded Q from loaded QL, written here as ΔH = ΔHL/ l+ß). Using this formula, the value of ΔH is very nearly constant over a wide range of values of ΔHL and ß. These quantities were varied on a given sphere by changing the angle ϕ between the RF and dc fields. We believe that this is the first time, with one sample and with no change of either surface finish or axis of magnetization, that ΔH has been shown to be independent of coupling- a necessary requirement for the method to be accurate. We conclude that the NRS method should be both practical and accurate over a wide range of ΔH.