(Invited) Magneto-Mechanical Micro-Nano Devices with Electrodeposited Magnetostriction Films
Authors: Ono Takahito 
Published: February 2024

Microsystems play an important role in IoT sensors and actuators in the recent information and communication society. Among these, actuators are important elements used in transmitters, acoustic devices, and optical elements, and for those devices, piezoelectric thin films have been used widely. Magnetostrictive materials are expected to have even greater actuation performance than that of the piezoelectric films, but in the magnetostrictive films integration technologies with a high performance have not yet been fully developed. We have developed the film deposition technologies for magnetostriction materials by electrodeposition and apply them to actuators and sensors [1,2].
The FeGa, TbDyFe, and FeCo magnetic materials are known as giant magnetostriction materials [3]. In this study, the film deposition method for these materials have been developed by electrodeposition. Tbe electrodeposition of rare earth elements is generally considered to be difficult, but in this study, by using Fe chelate as a catalyst, the magnetic films containing Fe and rare earth elements have been successfully deposited, and large magnetostriction are achieved. The TbDyFe films show magnetostriction of ~1000 [1]. In addition, large volume magnetostriction has been observed in these amorphous materials.
The magnetostrictive materials are known to have a reverse magnetostriction effect, in which the magnetization of the magnetic material changes when it is subjected to strain. They are known to work as strain sensors based on magnetic measurements. In order to demonstrate the strain sensing, a bi-material cantilever of FeGa/Si with a Si Hall sensor integrated on the support has been developed, as shown in Fig. 1 [2]. The vibration of the cantilever can be detected from the magnetization change using the integrated Hall sensor.
On the other hand, magnetostrictive actuators generally require an electromagnet to drive them, making them difficult to miniaturize the system. Therefore, an attempt has been made to drive magnetostrictive thin films by injecting spins into them using the spin Hall effect, giving angular momentum to the spins of magnetic materials and changing the spin fluctuations [4]. It is found that a large strain can be generated by spin injection into the TbDyFe film.
The above results show that high-performance magnetostrictive films can be deposited by electrodeposition and can be applied to strain sensors and spin-current driven actuators, and are expected to be applied to the development of novel sensors and actuators [5].
References

H. Shim, K. Sakamoto, N. Inomata, M. Toda, N. V. Toan and T. Ono, Magnetostrictive Performance of Electrodeposited TbxDy(1−x)Fey Thin Film with Microcantilever Structures, Micromachines 11, 5 (2020) 523.

T. Ezura, N. Inomata, T. Ono, Integration of Magnetostrictive Microsensor With Hall Element for Microstructure Resonant Detection, 21st International Conference on Solid-State Sensors, Actuators and Microsystems (Transducers), (2021) 418-421.

Mohammad Akita Indianto, Masaya Toa, Takahito Ono, Comprehensive study of magnetostriction-based MEMS magnetic sensor of a FeGa/PZT cantilever, Sensors and Actuators A 331, (2021) 112985.

H. Arisawa, H. Shim, S. Daimon, T. Kikkawa, Y. Oikawa, S. Takahashi, T. Ono, E. Saitoh, Observation of spin-current striction in a magnet, Nature Communication 13 (2022) 2400.

M. A. Indianto, M. Toda, T. Ono, Development of assembled microchannel resonator as an alternative fabrication method of a microchannel resonator for mass sensing in flowing liquid, Biomicrofluidics 14, (2020) 064111.

Figure 1