title: Surface lattice resonances and magneto-optical response in magnetic nanoparticle arrays.
abstract: Structuring metallic and magnetic materials on subwavelength scales allows for extreme confinement and a versatile design of electromagnetic field modes. This may be used, for example, to enhance magneto-optical responses, to control plasmonic systems using a magnetic field, or to tailor magneto-optical properties of individual nanostructures. Here we show that periodic rectangular arrays of magnetic nanoparticles display surface plasmon modes in which the two directions of the lattice are coupled by the magnetic field-controllable spin-orbit coupling in the nanoparticles. When breaking the symmetry of the lattice, we find that the optical response shows Fano-type surface lattice resonances whose frequency is determined by the periodicity orthogonal to the polarization of the incident field. In striking contrast, the magneto-optical Kerr response is controlled by the period in the parallel direction. The spectral separation of the response for longitudinal and orthogonal excitations provides versatile tuning of narrow and intense magneto-optical resonances.
authors.affiliation: NanoSpin, Department of Applied Physics, Aalto University School of Science, FI-00076 Aalto, Finland.
authors.forename: M
authors.initials: M
authors.lastname: Kataja
authors.affiliation: COMP Centre of Excellence, Department of Applied Physics, Aalto University, FI-00076 Aalto, Finland.
authors.forename: T K
authors.initials: TK
authors.lastname: Hakala
authors.affiliation: COMP Centre of Excellence, Department of Applied Physics, Aalto University, FI-00076 Aalto, Finland.
authors.forename: A
authors.initials: A
authors.lastname: Julku
authors.affiliation: COMP Centre of Excellence, Department of Applied Physics, Aalto University, FI-00076 Aalto, Finland.
authors.forename: M J
authors.initials: MJ
authors.lastname: Huttunen
authors.affiliation: NanoSpin, Department of Applied Physics, Aalto University School of Science, FI-00076 Aalto, Finland.
authors.forename: S
authors.initials: S
authors.lastname: van Dijken
authors.affiliation: COMP Centre of Excellence, Department of Applied Physics, Aalto University, FI-00076 Aalto, Finland.
authors.forename: P
authors.initials: P
authors.lastname: Törmä