An energy harvesting technology controlled by ferromagnetic resonance

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 as an energy harvesting technology by appropriately controlling the thermal conditions of the FM film.