salle 22-32-201
Sarah Mantion – Laboratoire Albert Fert, CNRS, Thales, Université Paris-Saclay
Abstract
Spin waves are elementary excitations within magnetic materials consisting of a phase-shifted precession of the magnetic moments of the material. Spin waves can transmit information, via their amplitude, frequency and/or phase. These waves offer several attractive advantages for device integration compared to standard electromagnetic waves such as scalability owing to their short wavelength in the microwave range (MHz to THz), frequency tunability by an applied magnetic field, non-reciprocity and non-linear effects, notably for the development of innovative microwave devices [1]. However, a few crucial challenges remain to be tackled for their potential integration in any microwave devices.
In this context, I will first present my PhD works on the study of Heusler based Co2MnSi (CMS) magnonic crystals reconfigurable at remanence. In analogy to photonic crystals, magnonic crystals are magnetic materials whose magnetic properties are periodically and artificially modified, which generates specific frequency band gaps in the spin waves dispersion. These micro/nanostructured systems can be used for passive microwave devices [2], however most of these devices present in the literature can be operated only under externally applied magnetic field, requiring the use of bulky and power hungry electromagnets. Studies are then conducted to develop magnonic devices that can be reconfigurable, i.e. that can offer different microwave responses that can be modified on purpose, at remanence (zero external magnetic field applied). In this work, we first demonstrated with micromagnetic simulations that the strong cubic crystal anisotropy in Co2MnSi thin films [3] allows the stabilization of different quasi-uniform remanent states depending on the direction of an applied initialization field in a magnonic crystal model system: a square magnetic antidot lattice with antidot sizes in the range 300 − 50 nm and for an aspect ratio lower than 1/3 [4]. In particular we demonstrated numerically and then experimentally via micro/nanofabrication and ferromagnetic resonance measurements of the CMS magnonic crystals that when a microwave signal is applied to such self-biased magnonic crystal, these different remanent states offer different microwave responses, one where the quantized and confined spin wave modes are well excited (« ON » state) and one where the latter are strongly attenuated (« OFF » state) [4,5].
In a second part, I will present to you some of our recent works towards the integration of magnonic components in analog microwave devices, and the strategy we are developing to optimize their radiofrequency response. I will take the example of reconfigurable magnonic delay lines [6] that I have been studying during my postdoc, and which are basic units for the realization of directional antennas. I will show you how the combination of analytical models [7], numerical models and device fabrication and characterization of magnonic YIG and CoFeB delay lines permit to optimize their frequency operation, bandwidth and insertion losses. To also achieve reconfigurable on-chip delay lines, I will present to you the approach based on MEMS technology that we investigate within the frame of the EU M&MEMS project [8]. Finally, I will discuss the possibility to develop magnonic devices operating at higher frequencies using antiferromagnetic systems, and discuss the properties of propagating spin-waves in canted antiferromagnets like α-Fe2O3 [9].
References
[1] A. V. Chumak et al., « Advances in Magnetics Roadmap on Spin-Wave Computing, » in IEEE Transactions on Magnetics, vol. 58, no. 6, pp. 1-72, June 2022, Art no. 0800172
[2] A V Chumak, A A Serga, and B Hillebrands. Magnonic crystals for data processing. Journal of Physics D: Applied Physics 50, 244001 (2017).
[3] I Abdallah, B Pradines, N Ratel-Ramond, et al. Evolution of magnetic properties and damping coefficient of Co2MnSi Heusler alloy with Mn/Si and Co/Mn atomic disorder. Journal of Physics D: Applied Physics 50, 035003 (2016).
[4] S. Mantion and N. Biziere. Cubic Anisotropy for a Reconfigurable Magnonic Crystal Based on Co2MnSi Heusler Alloy. Phys. Rev. Appl. 17, 044054 (4 2022).
[5] S. Mantion, A. Torres Dias, M. Madami, S. Tacchi, N. Biziere; Reconfigurable spin wave modes in a Heusler magnonic crystal. J. Appl. Phys. 7 February 2024; 135 (5): 053902.
[6] A. El Kanj, S. Mantion et al., in preparation
[7] H. Merbouche, Magnonic circuits based on nanostructured ultra-thin YIG for radiofrequency applications (Doctoral dissertation, Université Paris-Saclay) (2021).
[8] F. Maspero et al., « Magnetism meet microelectromechanical systems, » 2023 IEEE International Magnetic Conference – Short Papers (INTERMAG Short Papers), Sendai, Japan, 2023, pp. 1-2
[9] A. El Kanj et al., “Antiferromagnetic magnon spintronic based on nonreciprocal and nondegenerated ultra-fast spin-waves in the canted antiferromagnet α-Fe2O3”, Sci. Adv. 9, eadh1601(2023)
