Electrically Excited Inverse Electron Spin Resonance in a Split-Ring Metamaterial Resonator

Bianisotropic properties of the metamaterial built from split-ring resonators are utilized to excite electron-spin resonance in a gadolinium gallium garnet by the electric field of light. Surprisingly, the observed electron-spin resonance signal is seen as a maximum in the field-dependent transmittance, which indicates strong modifications of the metamaterial parameters in the coupled regime. In the geometry where both modes, electron-spin resonance and split-ring resonance, are active, the anticrossing regime can be observed. These effects can be explained using the classical model of two coupled oscillators and the bianisotropic properties of split-ring resonators.

Figure 1

Transmission (upper panel) and phase shift (lower panel) spectra of the split-ring resonators used in this work. Red circles—experimental geometry in which the resonance of the rings is excited by the electric ac field of the light ($\tilde{e}\parallel$ gap). Blue triangles—“silent” geometry in which no resonance is excited. The inset shows the geometry of the experiment and the arrangement of the rings.

Figure 2

Upper panel: Electron-spin resonance spectra of GGG in the classical geometry $\tilde{h}\perp B_0$ where the resonance is excited by the magnetic ac field of light. Lower panel: Transmission spectra of GGG with split-ring resonators and with $\tilde{h}\parallel B_0$. In this geometry no resonance is expected within classical condition.

Figure 3

Anticrossing of electron-spin and split-rings resonances. Upper panels: Typical transmittance spectra. Lower panel: Solid circles—positions of the resonances in the anticrossing regime. Open circles: resonance frequencies of pure GGG (see Fig. 2). Straight dashed lines represent the behavior of the resonances without coupling. Solid lines are drawn according to Eq. (2).