Experimental evidence for gyromagnetic damping in magnetic heads determined by impedance measurements up to 9 GHz

In this paper, we have developed an electrical circuit model of the impedance of an inductive write element that reproduces measured impedances to within 10% up to 9 GHz and allows interpretation in terms of the physical structure of the head. The model is used to extract the complex inductance of the magnetic yoke region of the head as a function of frequency, which is assumed to be linearly proportional to the yoke material permeability (after subtraction of the coil inductance). A clear negative excursion of the real part of the permeability is seen in the analysis, indicating gyromagnetic damping as the dominant loss mechanism, since eddy currents cannot produce a negative real part of the permeability.