Strong Magnon-Magnon Coupling in Two-Dimensional Diamond Shaped Ferromagnetic Nanodots Array

Abstract

Strong coupling between magnons and different quantum particles was studied extensively for quantum electrodynamics in the past few years. In this system, magnons in magnetic materials with high spin density are utilized where the “coupling strength” is collectively enhanced by square root of number of spins (N) to overcome the weaker coupling strength between individual spins and the microwave field. However, the strongly magnon-magnon [1] couplings in a confined nanomagnet remains to be revealed which is important for on chief intregration of hybride system. Here, we report the interaction between different magnon modes [2] in a magnetic dot array. The intermodal coupling in the strong coupling regime was approached with a maximum coupling strength of 0.745 GHz and cooperativity of 2.5. Furthermore, it is found that the coupling strength is highly dependent on the orientation of bias field. Micromagnetic simulation reveals that the compitetion between external bias field and inter dot dipolar interaction create a movement of domain in between the dot which results the anticrossing. The tunable coupling strength with the strength and orientation of bias field opens the opportunity of extremely controlled hybrid magnonic devices. This findings could greatly enrich the still evolving field of quantum magnonics.  Figure 1: (a) Bias field (Hext) dependent spin wave (SW) absorption spectra of NiFe nanodot lattice are shown at φ = 45°. (b) Distribution of internal at 400 Oe bias field strength along the 45 degree orientation (φ = 45°). The color map for the surface plots and internal field profile with the schematic of the external applied field (Hext) are given at the bottom right corner of the figure.