Tuning magnetic properties by microstructure control of nanocrys­talline thin films for compact vibration energy harvesters

Abstract

The vibration energy harvesting properties of Fe-based nanocrystalline soft magnetostrictive material (Fe-Si-B-P-Cu-C) thin films were systematically investigated. Thin films were deposited using rotational sputtering and subsequently annealed. Nanocrystallization occurred in the samples annealed at 100-110% of the crystallization temperature. This nanocrystallization process enhanced soft magnetic properties, however, decrease saturation magnetostriction reflecting the influence of the negative magnetostrictive α-Fe phase. The film annealed at 105% of the crystallization temperature exhibited the highest vibration power generation performance. This superior performance was attributed to the combination of enhanced soft magnetic properties, high saturation magnetic flux density, and a relatively large saturation magnetostriction.