Self-assembled, tightly packed spherical clusters of nanobeads have been shown to produce strong magnetic dipole resonances [1,2], with strong local hotspots that can be used for surface enhanced Raman scattering [3] and other applications. Here, we dynamically control the core diameter of these magnetic metamolecules using temperature-responsive hydrogel cores [4]. The synthetic route also allows for precise control of the number and size of the nanobead, their material, and can be used to produce heterogeneous versions of these dynamics metamolecules (DMMs) 5].<br/><br/>Here, we detail how variations in these parameters can affect the magnetic response of DMMs [6,7]. In large enough clusters, with large nanobeads, high-order magnetic multipole modes, i.e. magnetic quadrupole, octupole, and hexadecapole resonances, are observed in simulations as well as far-field extinction experiments [7]. We discuss the directional scattering cross-sections of DMMs, which can help their direct detection in experiments. Strong differences are observed between the forward- and backward-scattering cross-sections, due to mode-mixing of the broad magnetic dipole response and sharp higher-order magnetic resonances. This is an intrinsic property of these magnetic metamolecules and as such, their location can be precisely designed and dynamically controlled by temperature variations, for applications that involve enhancing the chiral polarizability of adsorbed materials.

Dynamically controlled high-order magnetic multipolar resonances in optical domain

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