Actuation performance of a microstructure with spin-current volume effect

Abstract

In this work, the actuation of micromechanical structures based on spin-current volume effect (SVE) using an amorphous magnetic film of Tb20Fe24Co56 (TFC) with volume magnetostriction (VM) is demonstrated, and the actuation performances are evaluated. A 2 mm-diameter circular polyimide diaphragm coated with thin TFC/non-magnetic metal (NM) films is prepared as the micromechanical structure, and Pt, Cu, and W are used as the NM film. When an AC charge current flows through the TFC/NM film on the diaphragm under an external magnetic field in the diaphragm plane and orthogonal to the charge current, an AC spin-current flows in the NM film due to the spin-Hall effect. In the SVE, the spin-current transports angular momentum from the NM to TFC films, which modulates the magnetization fluctuation of the TFC film due to the spin-transfer torque, causing the volume modulation based on spin-lattice coupling. Thus, this SVE can induce the mechanical actuation of micromechanical structures. The force generated by the SVE actuation is evaluated from the mechanical resonance of the diaphragm, and it is found that the power density of the diaphragm actuator with the TFC/Pt films is larger than 1.17×106 W/m3 at 20 mA peak-to-peak AC current under 0.72 T magnetic field. This SVE is effective as a new actuation mechanism for microsystems.