Frontier Research Institute for Interdisciplinary Sciences
Tohoku University

Energy harvesting is the technology of the generating electrical energy from wasted ambient energy, such as thermal energy, kinetic energy and windy energy. Because there are many small-scale energy sources that generally cannot be used, the energy harvesting has been recently receiving much attention. The common mechanisms for harvesting energy based on vibration are electrostatic, electromagnetic, piezoelectric and most recently magnetostrictive. In magnetostrictive materials, strain causes change in magnetization and magnetic flux density. The idea of the energy harvesting based on magnetostrictive material uses the change of magnetic field and generates electrical current throughout a pick-up coil. The magnetostrictive materials have advantages in the high mechanical strength and providing low impedance at the fundamental frequencies of common structural vibration sources.

Studies on the macroscopic fundamental properties of the piezoelectric and magnetostrictive materials have been carried out for a long time. However, it is very important to clarify the relationship between the microscopic lattice strain and the magnetic/electrical domain structure, and to control the macroscopic magneto/electrostriction due to the domain motion. The aim of the preset study is to establish the guideline of the materials design converting efficiently small vibration into electrical energy by focusing on BaTiO₃, Fe-Ga and Ni-Co-Mn-In.