biostudies-literatureYang WDepartment of Science and Technology of Sichuan Province (Sichuan Provincial Department of Science and Technology)Fundamental Research Funds for the Central UniversitiesMinistry of Science and Technology of the People’s Republic of ChinaNational Natural Science Foundation of ChinaMinistry of Science and Technology of the People's Republic of China (Chinese Ministry of Science and Technology)Foundation of CAEP Ultra-precision Machining Technology Key LaboratoryDepartment of Science and Technology of Sichuan ProvinceNational Natural Science Foundation of China (National Science Foundation of China)1719https://www.ebi.ac.uk/biostudies/studies/S-EPMC8971533biostudies-literatureUnknown13(1)Metamaterials with artificial optical properties have attracted significant research interest. In particular, artificial magnetic resonances with non-unity permeability tensor at optical frequencies in metamaterials have been reported. However, only non-unity diagonal elements of the permeability tensor have been demonstrated to date. A gyromagnetic permeability tensor with non-zero off-diagonal elements has not been observed at the optical frequencies. Here we report the observation of gyromagnetic properties in the near-infrared wavelength range in a magneto-plasmonic metamaterial. The non-zero off-diagonal permeability tensor element causes the transverse magneto-optical Kerr effect under s-polarized incidence that otherwise vanishes if the permeability tensor is not gyromagnetic. By reNature communicationsObservation of optical gyromagnetic properties in a magneto-plasmonic metamaterial.PMC8971533521023572018YFE0109200U19301142019YFH0154, 2021YFSY00165202100151972044Yang WQin JLiu QChen YYang RXia SLuo YDeng LWang HBi LDuan HfalseObservation of optical gyromagnetic properties in a magneto-plasmonic metamaterial.Metamaterials with artificial optical properties have attracted significant research interest. In particular, artificial magnetic resonances with non-unity permeability tensor at optical frequencies in metamaterials have been reported. However, only non-unity diagonal elements of the permeability tensor have been demonstrated to date. A gyromagnetic permeability tensor with non-zero off-diagonal elements has not been observed at the optical frequencies. Here we report the observation of gyromagnetic properties in the near-infrared wavelength range in a magneto-plasmonic metamaterial. The non-zero off-diagonal permeability tensor element causes the transverse magneto-optical Kerr effect under s-polarized incidence that otherwise vanishes if the permeability tensor is not gyromagnetic. By re2022-01-01T00:00:00Z2022 Mar2025-04-19T17:37:12.366Z2025-04-19T17:37:12.366ZS-EPMC89715333536177710.1038/s41467-022-29452-9