▎ 摘　　要

NOVELTY - The device has two rectangular strips (201) that are coplanar and include a space between the two. Two of the rectangular strips include different aspect ratios, n is a natural number and n is greater than or equal to 3. The material of the rectangular strips is graphene. The surface of a structure layer (20) excites a surface plasmon effect under circularly polarized light irradiation. The direction of the charge on the surface of the structure layer is changed, so that the refractive index of the structure layer is different under the irradiation of left-handed and right-handed circularly polarized light after applying an external magnetic field to the structural layer. The transmittance of the structure layer does not different under the illumination of left-handed and right-handed circularly polarized light. The difference in transmittance is used to reflect the size of the magnetic field, and the measurement of the magnetic field is realized. USE - Measuring device for magnetic field. ADVANTAGE - The transmittance of the structure layer is different under the illumination of left-handed and right-handed circularly polarized light, so that the difference in transmittance is used to reflect the size of the magnetic field, thereby realizing the measurement of the magnetic field. The device uses the change of the optical signal to reflect the size of the magnetic field, so the sensitivity of the magnetic field measurement is greatly improved. DESCRIPTION OF DRAWING(S) - The drawing shows a schematic diagram of the measuring device for magnetic field. Substrate layer (10) Structure layer (20) Rectangular strip (201)