The emergence of the Internet of Things (IoT) devices, one of the crucial building blocks of modern technologies, shows of late a remarkable interest in the field of microwave-based technologies, e.g., RF energy harvesting, radars, miniaturized antennas, ultra-low field magnetic sensors etc. 1-5. The voltage-controlled microwave oscillators typically consume a large amount of power to produce microwave frequencies with moderate frequency stabilities. The conventional batteries cannot be used for powering such power-hungry IoT devices and prohibitory cost for replacement in wireless sensor nodes (WSN), particularly in inaccessible locations and their sustainability due to the overall pollution they are likely to produce. Hence, researchers are looking to invent state-of-the-art microwave oscillators 5 for such cutting-edge applications. In this work, we report the domain wall movement in the patterned array of rectangular magnetostrictive nanomagnets/piezoelectric heterostructures caused by surface acoustic waves (SAW) for microwave generation. A surface acoustic wave launched on the substrate produces periodic strain within the patterned nanomagnets, which, in turn, stimulates the magnetization precession of the nanomagnets resulting in different magneto-dynamical resonance modes in the array of nanomagnets with a rich spin wave (SW) texture. The generated SWs (magnons) further interact with the EM wave radiation (photons) at the SAW frequency 6; this phonon-magnon-photon coupling generates a 0.56 GHz microwave frequency with a 13.9 MHz linewidth and Q-factor of 40. The generated non-volatile spin textures of the nanowires are also useful in energy-efficient logic and low-power computing applications 7. References Acknowledgement: Both, AS and SR gratefully acknowledge the financial support for this work from the "EU-H-2020" project, “EnABLES-JRA”, Project ID: 730957.
References:
1 T. Nan, H. Lin, Y. Gao, Nature Communications 8, 296 (2017).
2 J.-S. Kim, M.-A. Mawass, A. Bisig, Nat. Commun. 5, 3429 (2014).
3 T. Ono and Y. Nakatani, Appl. Phys. Express 1, 61301 (2008).
4 R. Sbiaa, M. Al Bahri, and S. N. Piramanayagam, J. Magn. Magn. Mater. 456, 324 (2018). 5 S. Bhatti and S. N. Piramanayagam, Phys. Status Solidi – Rapid Res. Lett. 13, 1800479 (2019).
6 R. Fabiha, J. Lundquist, S. Majumder, Advanced Science 9, 2104644 (2022).
7 V. Sampath, N. D’Souza, D. Bhattacharya, Nano Letters 16, 5681 (2016).

(a)Initial magnetization configuration of NWs; l, w, are length, width of each NWs along the x, y directions, respectively, and s is the spacing between the NWs in xy plane.(b)The multidomain state with transverse stress.(c)The multidomain structures in (b) vanished upon launching of SAW.(d)Final spin structure after completion simulation, retaining the domain structure in (c).

Power distribution as a function of spacing between the neighbouring NWs along x, y, z directions in (a), (b), (c), respectively.