Application of electroplated Ni–Fe thick film to magnetostrictive material in vibration power generator

Ni100−xFex (at. %) films of about 37 μm thickness are electroplated on Cu base plates of 50 mm length, 10 mm width, and 300 μm thickness by varying the composition from x = 0 to 99. They are applied to cantilevers in magnetostrictive vibration power generators. The influences of magnetic and magnetostrictive properties of electroplated film on the vibration power generation property are systematically investigated. The films with x = 41–65 show low coercivities of about 4 Oe reflecting the low magnetocrystalline anisotropy constants. Large negative magnetostriction is recognized for the films with x = 0–14, whereas large positive magnetostriction is observed for the films with x = 57–80. The cantilevers are vibrated at the respective resonance frequencies of about 105–115 Hz and with the acceleration of 1.5 G while applying the bias magnetic field in a range of 0–300 Oe along the length direction. The output voltages are detected by using a coil with 8000 turns. Peak voltages higher than 1 V are obtained for the films with x = 61–65 whose coercivities are low and magnetostrictions are large. The present study has shown that an Ni–Fe film not only with large magnetostriction but also with low magnetic anisotropy constant is useful as the magnetostrictive material in vibration power generator.