Highly sensitive magnetometry method based on the magnetoplasmonic crystal

A novel concept of the room-temperature magnetoplasmonic magnetic field sensor with high sensitivity and spatial resolution is presented. The advanced flux-gate technique is used. Magnetization of the fully saturated magnetic film is rotated in the film plane and the monitored magnetic field is measured by detecting variation of optical transmittance through the sensing element. The sensing element is a magnetoplasmonic crystal consisting of a gold grating with subwavelength period deposited on a thin transparent dielectric film of bismuth substituted iron-garnet. Geometrical parameters of the magnetoplasmonic crystals are adjusted to have pronounced resonances of the longitudinal magneto-photonic intensity effect (LMPIE). The experimental study revealed that such approach allows one to reach the 2nT sensitivity level which was limited by the noise of the laser. The demonstrated magnetoplasmonic magnetometry method is promising for mapping and visualization of ultra-small magnetic fields.