Magnetostrictive Fe-Co-B Alloys for High-frequency Sensor Applications

Magnetostrictive materials with a soft magnetic response are the fundament for the development of some high performance sensors and actuators. Fe-Co-B was identified as a potential candidate for the development of high-frequency sensors and actuators. The key for using it is the preparation of Fe-Co-B thin film in proper microstructure and composition. In this study, electrochemical process is used to prepare the Fe-Co-B thin film under different conditions. The microstructure, magnetic and magnetostrictive properties of the thin film were characterized. The influence of the deposition condition and the solution concentration on the microstructure of the film was determined. Thin films with similar thickness deposited under low current density exhibited different structure from those deposited at higher current densities. It was due to the different elemental deposition rate at different current densities. At same current density, the thin films showed similar structure. Fe-Co-B thin films were soft magnetic materials. The hysteresis loop exhibited very slim indicating a novel soft magnetic property. It is known that the detection sensitivity of sensor depends on the size the sensor. The smaller the sensor is, the higher the sensitivity is. Additionally, the smaller the size, the higher the resonance frequency is. To get the sensor with higher sensitivity for higher frequency application, the micro/nano size sensors are needed. By combining the microfabrication method with electrochemical process, the miniaturized magnetostrictive sensors and actuators are prepared. The magnetostrictive thin film with a high sensor performance was obtained. Recently, micro strips with size of about 500 µm (lengh) × 100 µm (with) × (2~10 µm) (thickness) have been synthesized. The strips exhibited strong resonance frequency.