This dataset includes the COMSOL modelling files, raw spectra data, raw MOKE data, and the processed data.The article associated with this dataset is located in ORE at: http://hdl.handle.net/10871/33084This is the dataset used for the Loughran et al. (2018) article "Design and fabrication of plasmonic cavities for magneto-optical sensing" published in AIP Advances.Engineering and Physical Science Research Council (EPSRC) grants EP/1038470/I and EP/1038411/