Strain and Magnetic Field Changes in Vibration of Devices Attached Iron Alloys with Large Magnetostriction

Abstract

To understand the mechanism of vibration energy harvesting using magnetostrictive Fe-Ga alloys, the dynamic strains at different locations of a U-shaped device during vibration were simulated. In the simulations, the previous results for location-dependent strain in the vibration experiments were fitted with trigonometric functions. The results show that the amplitude and phase of the strain vary with location, and that the electromagnetic force is generated at different locations. Since magnetic induction is thought to occur due to an external magnetic field, the magnetic domain structure near the cube orientation of Fe-Ga alloy single crystals was observed using a Kerr effect microscope. As a result, Bloch magnetic domain structures with different contrasts of brightness and darkness were observed depending on the applied magnetic field. It was shown that striped magnetic domains were dominant when the applied magnetic field was small, while lancet magnetic domains oriented to the magnetic field appeared with transverse straight supplementary domains as a magnetic domain under a saturated magnetic field. The domain patterns in one direction magnetic fields were not necessarily the same as those observed in the opposite direction. This indicates that Fe-Ga alloy single crystals are used as a core for vibrational energy harvesting. Also, the motion of magnetic walls is thought to play an important role in the vibrational properties of the material, and inhomogeneous elastic strain associated with magnetic domains evolves microscopically in single crystals.