Presentation Information
[P2-48]A novel approach to fabricate Sm-Co micro-magnets and its microstructure
Muni Bhaskar Siva Kumar1, *Taisuke Sasaki1, Ryogen Fujiwara2, Hossein Sepehri-Amin1, Mio Otsuru2, Yoshinori Fujikawa2, Tadakatsu Ohkubo1 (1. National Institute for Materials Science (Japan), 2. TDK Corporation (Japan))
Keywords:
Sm-Co magnets,Micromagnets,Microstructure
Micro-Electro-Mechanical Systems (MEMS) and other micro-scale devices, such as micro-actuators and motors etc., are used in diverse applications in consumer electronics, Internet of Things (IoT) networks, and biotechnology. Although high performance micromagnets are essential in these applications, conventional processes, such as sintering and hot deformation, are not suitable for manufacturing the micromagnets. To date, challenges have been made to fabricate the micromagnets using various processes such as sputtering, electrodeposition, pulsed laser deposition etc. Another potential approach to fabricate the micromagnets is to exploit the reaction diffusion that occurs in the fabrication of SmCo5 powders by the reduction-diffusion process. This presentation will introduce a simple approach to the fabrication of the micromagnet, i.e., reaction between Sm molten salt and Co-plate followed by annealing and discuss its feasibility in terms of the microstructure and property.
A Co-thin plate was immersed into a Sm-molten salt at 700 °C. The sample was subsequently annealed at 940 °C. The microstructure of the samples was analyzed using a scanning electron microscope (SEM), (scanning) transmission electron microscope ((S)TEM), and magneto-optic Kerr effect (MOKE) microscope. The magnetic properties of the samples were evaluated using vibrating sample magnetometer (VSM).
A uniform SmCo2 layer forms on the surface of the Co-plate after the immersion into the Sm-molten salt at 700 °C.The subsequent annealing at 940 °C facilitates the diffusion of Co and its reaction with SmCo2, resulting in the sequential nucleation and well-defined columnar growth of Sm2Co17, SmCo5. and Sm2Co7 layers. Among these layers, the growth rate of the SmCo5 layer is faster than the other layers, and electron backscattered diffraction (EBSD) analysis showed that the <0002> axis of the SmCo5 grains is strongly aligned to the film normal direction. The 60 h annealed sample shows a dominant SmCo5 layer and exhibits the highest coercivity of ~ 0.6 T by VSM. A prolonged annealing up to 100 h resulted in a significant loss of coercivity to ~ 0.1 T probably due to a slight increase in the Co content. These results suggest that the optimization of the process parameters such as the thickness of the Co-plate and the conditions for the immersion into the molten Sm and the subsequent annealing will open up a possibility for the fabrication of the SmCo5 micromagnets.
A Co-thin plate was immersed into a Sm-molten salt at 700 °C. The sample was subsequently annealed at 940 °C. The microstructure of the samples was analyzed using a scanning electron microscope (SEM), (scanning) transmission electron microscope ((S)TEM), and magneto-optic Kerr effect (MOKE) microscope. The magnetic properties of the samples were evaluated using vibrating sample magnetometer (VSM).
A uniform SmCo2 layer forms on the surface of the Co-plate after the immersion into the Sm-molten salt at 700 °C.The subsequent annealing at 940 °C facilitates the diffusion of Co and its reaction with SmCo2, resulting in the sequential nucleation and well-defined columnar growth of Sm2Co17, SmCo5. and Sm2Co7 layers. Among these layers, the growth rate of the SmCo5 layer is faster than the other layers, and electron backscattered diffraction (EBSD) analysis showed that the <0002> axis of the SmCo5 grains is strongly aligned to the film normal direction. The 60 h annealed sample shows a dominant SmCo5 layer and exhibits the highest coercivity of ~ 0.6 T by VSM. A prolonged annealing up to 100 h resulted in a significant loss of coercivity to ~ 0.1 T probably due to a slight increase in the Co content. These results suggest that the optimization of the process parameters such as the thickness of the Co-plate and the conditions for the immersion into the molten Sm and the subsequent annealing will open up a possibility for the fabrication of the SmCo5 micromagnets.
