Flexible electronics has been widely studied for the future applications, such as flexible display, wearable health care device and electronic skin for robots 1-2. In particular, the stress effect on the thin film is a key element to develop magnetic sensors and actuators. Permalloy is well known material for the flexible applications due to its very low magnetostriction under the stress 3.
In this study, we have measured the mechanical magnetostriction effect on the Permalloy thin film and dot array patterns, where the aspect ratio (length/width) varied 0.5, 1.0, and 2.0, as shown in Figure 1. The width of the dot array was fixed as 10 μm. The stress anisotropy field was measured using ferromagnetic resonance (FMR) method and calculated by Kittel model. The FMR signals depending on the aspect ratio of the dot array are shown in Figure 2, where the excitation microwave frequency was 6 GHz. The stress anisotropy field was significantly affected by the bending repetition and the curved direction with the shape of the dot arrays. The details of the experimental and results will be discussed.
References:
1 A. Nathan, A. Ahnood, M.T. Cole, S. Lee, Y. Suzuki, P. Hiralal, F. Bonaccorso, T. Hasan, L. Garcia-Gancedo, A. Dyadyusha, S. Haque, P. Andrew, S. Hofmann, J. Moultrie, D. Chu, A.J. Flewitt, A.C. Ferrari, M.J. Kelly, J. Robertson, G.A.J. Amaratunga, and W.I. Milne, Proc. IEEE 100, 1486 (2012).
2 R. Dahiya, N. Yogeswaran, F. Liu, L. Manjakkal, E. Burdet, V. Hayward, and H. Jörntell, Proc. IEEE 107, 2016 (2019).
3 R. Bonin, M. Schneider, T. Silva, and J. Nibarger, J. Appl. Phys. - J APPL PHYS 98, (2005).

Figure 1. Permalloy dot arrays, where the aspect ratio varied 0.5 (a), 1.0 (b), and 2.0 (c).

Figure 2. Ferromagnetic resonance signals depending on the aspect ratio of the dot arrays.