  We have successfully demonstrated electrical charging using the electromotive
force (EMF) generated in a ferromagnetic metal (FM) film under ferromagnetic
resonance (FMR). In the case of Ni80Fe20 films, electrical charge due to the
EMF generated under FMR can be accumulated in a capacitor; however, the amount
of charge is saturated well below the charging limit of the capacitor.
Meanwhile in the case of Co50Fe50, electrical charge generated under FMR can be
accumulated in a capacitor and the amount of charge increases linearly with the
FMR duration time. The difference between the Ni80Fe20 and Co50Fe50 films is
due to the respective magnetic field ranges for the FMR excitation. When the FM
films were in equivalent thermal states during FMR experiments, Co50Fe50 films
could maintain FMR in a detuned condition, while Ni80Fe20 films were outside
the FMR excitation range. The EMF generation phenomenon in an FM film under FMR
can be used an energy harvesting technology by appropriately controlling the
thermal conditions of the FM film.
