We demonstrate a lossless switching between vortex and collinear magnetic states in circular FePd disks arranged in a square lattice. Above a bifurcation temperature ( ) T e we show that thermal fluctuations are enough to facilitate flipping between the two distinctly different magnetic states. We find that the temperature dependence of the vortex annihilation and nucleation fields can be described by a simple power law relating them to the saturation magnetization.The experimental observation of the magnetic vortex state in circular islands [1] has attracted substantial interest within the field of nanomagnetism [2][3][4][5][6][7][8][9]. The range of envisioned applications is extensive, spanning from memory devices [10] to targeted cancer-cell destruction [11]. A magnetic vortex has four states defined by the polarity, the direction of

We reveal an explicit strategy to design the magneto-optic response of a magneto-plasmonic crystal by correlating near- and far-fields effects. We use photoemission electron microscopy to map the spatial distribution of the electric near-field on a nanopatterned magnetic surface that supports plasmon polaritons. By using different photon energies and polarization states of the incident light we reveal that the electric near-field is either concentrated in spots forming a hexagonal lattice with the same symmetry as the Ni nanopattern or in stripes oriented along the Γ-K direction of the lattice and perpendicular to the polarization direction. We show that the polarization-dependent near-field enhancement on the patterned surface is directly correlated to both the excitation of surface plasmon polaritons on the patterned surface as well as the enhancement of the polar magneto-optical Kerr effect. We obtain a relationship between the size of the enhanced magneto-optical behavior and the polarization and wavelength of optical excitation. The engineering of the magneto-optic response based on the plasmon-induced modification of the optical properties introduces the concept of a magneto-plasmonic meta-structure.

Surface plasma resonance (SPR) excitation in a Co-based two-dimensional magnetoplasmonic crystal was found to strongly enhance the second-harmonic generation (SHG) efficiency. Large changes in the phase shift between magnetic and nonmagnetic SHG contributions were observed in the transversal Kerr effect as a function of the incidence angle. The activation of a nonlocal quadrupole mechanism of the magnetic SHG due to the SPR excitation was found to lead to an unusual phase behavior in the vicinity of the resonance.

Extraordinary optical transmission is observed due to the excitation of surface plasmon polaritons in 2-dimensional hexagonal anti-dot patterns of pure Ni thin films, grown on sapphire substrates. A strong enhancement of the polar Kerr rotation is recorded at the surface plasmon related transmission maximum. Angular resolved reflectivity measurements under an applied field reveal an enhancement and a shift of the normalized reflectivity difference upon reversal of the magnetic saturation (transverse magneto-optical Kerr effect-TMOKE). The change of the TMOKE signal clearly shows the magnetic field modulation of the dispersion relation of SPPs launched in a 2D patterned ferromagnetic Ni film. Magneto-plasmonics offer unique possibilities to manipulate light by the use of external magnetic fields. [1][2][3][4] The prevailing choice of materials for fabrication of magnetoplasmonic structures has been combined structures of noble and magnetic metals/dielectrics, such as Au and Co/Iron garnet. 1,5,6 The basic idea behind this choice is the combination of the large plasmon activity of noble metals with the magnetic functionality provided by the additional materials. Another reason for the use of noble metals is the excellent resistance to oxidation, which is required to obtain durable patterned thin films. Ni is an interesting candidate in this context as it forms a thin and self-passivating oxide layer (approximately 1 nm). 7,8 Furthermore, the magneto-optical activity of Ni-based nano-patterns can be enhanced by the presence of surface plasmon polaritons (SPPs). [9][10][11][12][13] The magnetic field can provide the means for control of SPPs, as it has been predicted for noble metals, 14 and explored experimentally in hybrid structures. 2,5,6 Early studies on this effect were targeted towards semiconductor-based SPPs (Ref. 15) but not in metallic systems, where high magnetic fields are required. 16 In pure magnetic materials, the need for high fields is not present as the magneto-optical effects are sufficiently strong.In this Letter, we discuss the influence of an external magnetic field on the SPPs for the case of a pure magnetic metal, such as Ni, patterned in two-dimensions (2D) on a transparent substrate. We examine to what extent the ferromagnetic Ni can be used as a host material for SPPs. We show that the magnetic field induces a modulation of the dispersion of SPPs excitation in Ni.A Ni anti-dot sample was prepared on a double side polished Al 2 O 3 ½11 20 substrate. The patterning was accomplished by the use of self-organization of colloidal polystyrene beads as shadow masks. 9 A 30 nm thick Ni film was deposited on the masked sapphire substrate, using electron-beam evaporation. A snapshot of the procedure is illustrated in Fig. 1, where both the shadow mask and the resulting holes are clearly seen. This process resulted in a well defined Ni layer, decorated by holes of a diameter d ¼ 300 nm, spaced on an hexagonal lattice of periodicity of a ¼ 450 nm. The ratio of the radius to pitch size was determined t...

The influence of surface plasmons on the magneto-optic activity in a two-dimensional hexagonal array is addressed. The experiments were performed using hexagonal array of circular holes in a ferromagnetic Ni film. Well pronounced troughs are observed in the optical reflectivity, resulting from the presence of surface plasmons. The surface plasmons are found to strongly enhance the magneto-optic response (Kerr rotation), as compared to a continuous film of the same composition. The influence of the hexagonal symmetry of the pattern on the coupling between the plasmonic excitations is demonstrated, using optical diffraction measurements and theoretical calculations of the magneto-optic and of the angular dependence of the optical activity.