Electron-Beam-Conditioned Magnetic-Dipole Emission in Cathodoluminescence

Accessing the magnetic-dipole (MD) optical response in nanoscale structures is a longstanding goal in photonics because magnetic modes enable low-loss and interference-rich control of light. In practice, MD signatures are often mixed with electric dipole and higher-order radiation, making selective radiative emission difficult. Here we show that aloof fast-electron cathodoluminescence (CL) provides an electron-beam-conditioned route to MD-dominated emission from core-shell nanoparticles. Through multipolar CL analysis, guided synthetic index design, and real-material refinement, we identify conditions under which the MD becomes the dominant radiative channel in CL. The beam-conditioned optimum differs from the conventional optical plane-wave benchmark, showing that electron-beam excitation can access nanoparticle mode structure in a distinct way. These results connect ideal magnetic-dipole scattering concepts to aloof-electron cathodoluminescence and provide a design route for identifying magnetic-dipole-favored radiative emission from core-shell Mie resonators.