Survey of Permanent Magnet for a Laser-Assisted Heating Magnetization to Generate Designed Surface Magnetic Flux Density Distribution for Magnetic Mems Devices

To realize high-performance micro magnetic devices such as energy harvesters and micro actuators, a fine-pitch and multi-pole magnetization method for permanent magnets are required to reduce the self-demagnetizing field in the magnet and increase the surface magnetic flux density. We are developing a multi-pole micro magnetization method that combines a local coercivity reduction of the permanent magnet by laser-assisted heating with an external reverse magnetic field. However, the designed surface flux density has not been obtained. Using the proposed magnetization method, we have experimentally investigated the relationship between magnet material and magnetization results. Experimental results show that using highly heated resistant magnets produces the surface flux density of the permanent magnets closer to the design values.

Introduction

Fine-pitch and multi-pole magnetization is necessary to reduce the self-demagnetizing field of permanent magnets and to increase the surface flux density to realize the high performance of micromagnetic actuators and magnetic energy harvesters. In the previous research, an actuator with a high force density of 0.96 mN/A⋅mm³ was achieved by segmenting a monolithic unidirectionally magnetized magnet into multi-pole magnets on a chessboard and combining them with micro coils [1]. However, for even higher performance, a multi-pole micro-magnetized monolithic magnet is required, as shown in Figure 1, which can enhance the surface magnetic flux density and expand the force-generating area by removing the dead space.