The shape-dependent demagnetizing field in ferromagnetic resonance

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Abstract
Ferromagnetic resonance has been observed at 9.23 GHz in a series of nickel disks of diameter 5 mm and thickness between 0.1 and 1.6 mm. The variation of the resonance field in both the parallel and perpendicular orientations is compared with that calculated using the demagnetizing factors obtained from (i) the theory of Osborn (1945) for ellipsoidal samples and (iii) that of Joseph and Schlomann (1965) for nonellipsoidal samples. Good agreement with the former is obtained for disks of aspect ratio down to 5. An extra signal is observed in the perpendicular orientation, and this is shown to come from the edge of a disk. A qualitative explanation of the variation of this signal with disk thickness is provided.