Angular Control of a Hybrid Magnetic Metamolecule Using Anisotropic FeCo

Abstract

By coupling magnetic elements to metamaterials, new hybrid metamolecules can be created with interesting properties such as photo-magnon coupling. Here, we present results for a hybrid metamolecule, using a hard as opposed to soft magnetic material. This was achieved by placing a thin film of single crystal hard FeCo in close proximity to a split ring resonator (SRR). To suppress eddy-current shielding the FeCo film was patterned into 100 µm disks. The resulting metamolecule exhibits photon-magnon coupling when the FeCo is on resonance (FMR). Three new features are demonstrated and discussed. One, hard magnets allow FMR to be performed in near zero field, thereby partially eliminating the need for applied fields. Two, because the FMR is anisotropic, angular control over hybrid SRR/FMR resonances is achieved. Three, the single crystal FeCo can be re-magnetized parallel/perpendicular to the plane of the SRR, in real time, thus opening the door to magnetically configurable metamaterials. Finally, the work was performed using coplanar waveguide (CPW) excitation. A study was made therefore of how best to excite the numerous transverse magnetic (TM) and transverse electric (TE) modes of the SRR, using near-field CPWexcitation. Such detail is important, if the strongest signals are to be achieved. Photon-magnon coupling strengths of up to 5% are demonstrated.

Hybrid Resonance Memory Metamaterial with Full‐Wave Operation

“…After m‐MW stimuli, the S 21 showed a significant change in the range of f m = 1.5–2.5 GHz. The observed changes can be explained from the N‐FMR frequency shift by m‐MW stimuli, and from characteristic phenomenon of the resonance hybridization: splitting, broadening, and shifting of resonance modes . In the YIG/metamaterial system, when the N‐FMR frequencies of the YIG and metamaterial resonance are close to each other, two intense resonance modes appear at a lower and a higher frequency region by the resonance hybridization.…”

“…The N‐FMR is determined by the MD structure that depends on the history of applied input microwave signals, and therefore, L h and R h show the memristive behavior for the input microwave signals. One can describe the memristive resonance of the coupled resonator by solving these equations, where the ω r,h and Q ‐factor describe the change of hybrid resonance, such as a splitting of the resonance modes, a resonance frequency shift, and a broadening of the resonance linewidth …”

“…Various natural memory materials have been applied to implement the memory metamaterials, however, there has been no study on the memory metamaterial based on the ferromagnetic materials to the best of our knowledge. Although the metamaterial (resonator, or cavity)‐ferromagnetic hybrid systems have been studied extensively due to their distinct properties resulting from a strong resonance hybridization, the studies have been focused on the hybrid resonance occurring in a magnetically saturated state by a static external magnetic field, where the hybrid resonance disappears whenever the external magnetic field is removed.…”

Expanding the Lorentz concept in magnetism

“…In recent years there has been growing interest into incorporating thin magnetic films (100 μm-100 nm) into metamolecules [1][2][3][4] and magnonic devices [5,6]. The properties of thin patterned magnetic films are therefore of importance.…”

“…In essence, the work presented here can be seen as an attempt to identify that shape of film (pattern) which should yield the narrowest FMR linewidth. Such experiments should have relevance in magnetic hybrid split ring resonator (SRR) metamolecules, where strong photon-magnon coupling occurs [2][3][4]. In the latter experiments, the permalloy and other magnetic films were simply patterned into small circular disks of ∼100 μm diameter, primarily to suppress eddy currents.…”