Electron spin resonance study of mixed Bi₂Se₃ topological insulator–magnetic insulator nanoparticles

We investigated Bi₂Se₃ topological insulator nanoparticles mixed with room-temperature ferromagnetic insulator nanoparticles by using electron spin resonance (ESR) of the surface conduction electrons in the Bi₂Se₃ nanoparticles. The ESR intensity and linewidth as a function of the molar ratio of the magnetic insulator could be well understood in terms of the magnetic proximity effect due to the short-range exchange field of the magnetic insulator nanoparticles along with the long-range magnetic dipole field effect and the surface-to-volume ratio effect.