Enhancing ferromagnetic resonance absorption for very thin insulating magnetic films with spin plasmonics

• Published in: Journal of applied physics 2015-05, Vol.117 (18)
• Main Author: Chui, S. T.
• Format: Article
• Language: English
• Subjects: ABSORPTION; Adaptive control; BRILLOUIN EFFECT; CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; Damping; DIELECTRIC MATERIALS; Dielectrics; DIFFUSION LENGTH; FERRITE GARNETS; Ferromagnetic materials; FERROMAGNETIC RESONANCE; Gadolinium; GADOLINIUM COMPOUNDS; Gadolinium-gallium garnet; GALLIUM OXIDES; Group velocity; INTERFACES; IRON OXIDES; LAYERS; LINE WIDTHS; Magnetic films; Magnetic permeability; MAGNETIC SURFACES; MAGNETIC SUSCEPTIBILITY; Photonics; Plasmonics; Resonance absorption; SPIN; SUBSTRATES; THIN FILMS; Yttrium; YTTRIUM COMPOUNDS; Yttrium-iron garnet
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/1.4919745

We consider enhancing the ferromagnetic resonance (FMR) absorption of very thin insulating magnetic films by placing it on top of a dielectric. We find that the signal is enhanced by at least an order of magnitude due to a new nonreciprocal interface resonance that is a mixture of the magnetic surface plasmon mode and a wave guide mode. This resonance occurs over a wide range of thicknesses of the dielectric that is still much less than the wavelength and is made possible by the negative magnetic susceptibility of the magnetic layer. The line width of absorption is reduced by an order of magnitude less than the Gilbert damping parameter. At some frequency, the group velocity of this resonance is negative. Experimentally, very thin yttrium iron garnet (YIG) films are grown on a Gadolinium Gallium Garnet (GGG) substrate which can be considered the dielectric. Our model applies to experiments performed in the YIG/GGG system. Indeed, our picture resolves the disagreement on the magnitude of the spin diffusion lengths obtained with the FMR and the Brillouin scattering techniques. It also provides for a way to make new adaptive thin film miniaturized photonic nonreciprocal devices with low loss.