split-ring resonator

A split-ring resonator (SRR) is an artificial structure used in metamaterials. These structures are smaller than the wavelengths of electromagnetic radiation they interact with. SRRs, often consisting of rings or squares with a gap, are engineered to control a material's magnetic permeability. When exposed to an oscillating magnetic field at their resonant frequency, they generate an electric current that creates a magnetic dipole moment. This induced moment can be adjusted to be in or out of phase with the external field, allowing for the engineering of negative magnetic permeability, a property not found in nature. This capability is crucial for creating materials with unique electromagnetic properties, such as a negative refractive index.1