Magnetoplasmonic crystals are spatially periodic nanostructured magnetic surfaces combining the features of surface plasmon polariton excitation and magneto-optical tunability. Here we present a comprehensive experimental and theoretical work demonstrating that in magnetoplasmonic crystals the coupling of free space radiation to surface plasmon polariton modes in conjunction with the inherent magneto-optical activity, enable cross-coupling of propagating surface plasmon polariton modes. We have explored the consequences of this unique magnetoplasmonic crystal optical feature by studying the light reflected from a two-dimensional periodic array of cylindrical holes in a ferromagnetic layer illuminated at oblique incidence and magnetized in the sample plane, namely, in the so-called longitudinal Kerr effect geometry. We observe that the magneto-optical spectral response arises from all the excitable surface plasmon polariton modes in the magnetoplasmonic crystal irrespective of the incoming light polarization. We show that this is a direct consequence of the magneto-optically mediated coupling of propagating surface plasmon polariton modes. We demonstrate that a large enhancement of the longitudinal Kerr effect is induced when special noncollinear surface plasmon polariton modes, which couple to both p- and s-polarized light, are resonantly excited. We show how the resonant enhancement of the Kerr effect can be set at desired radiation wavelengths and incidence angles by precise plasmonic band engineering achievable through the proper design of the magnetoplasmonic lattice structure. Our findings, besides clarifying the underlying physics that governs the peculiar magneto-optical properties of magnetoplasmonic crystals, open a path to the design of novel active metamaterials with tailored and enhanced magneto-optical activity.

Multiferroic thin films with the general formula BiFe1−xScxO3 (x=0.0, 0.1, 0.3, and 0.5mol%) (BFS) were synthesized on Pt∕Ti∕SiO2∕Si substrates through a sol-gel deposition method. From the x-ray diffraction (XRD) analysis, it was observed that the unit cell volume increased upon Sc doping up to 0.3mol%. Impure phase appeared for the BFS (Sc: 0.5mol%) films. Leakage current, ferroelectric, and magnetic properties were also found to improve for Sc doping up to 0.3mol%. Room temperature magnetic coercive field for in-plane orientation of films showed the lowest value for BFS (Sc: 0.3mol%) films, which indicates that BFS (Sc: 0.3mol%) films were more magnetically soft. Room temperature value of the magnetodielectric effect in the presence of magnetic field of 8kOe was found to have maximum of 3.36% for the BFS (Sc: 0.3mol%) films. From the x-ray photoelectron spectroscopy measurements, it was observed that the Fe has mixed valency states of 2+ and 3+. The ratio of Fe2+ and Fe3+ was found to decrease slightly in BFS (Sc: 0.3mol%) films. The improved leakage current and M-H loops support the authors’ observation.

We present a systematic study of the structural, magnetic, and magnetotransport properties of Co-doped Fe3O4 films deposited on MgO (100) substrates by cosputtering technique. Transmission electron microscopy images suggest that the undoped and Co-doped Fe3O4 films are polycrystalline in nature and consist of a well defined grain boundary network. The temperature dependence of resistance also shows that the transport mechanism in our films is dominated by electron tunneling across antiferromagnetically coupled grain boundaries. We observed that the magnetic properties of the doped films are markedly sensitive to the Co doping concentration, with the magnetization curves showing drastic changes in coercivity with increasing doping concentration. In-plane magnetoresistance curves show linear magnetic field dependence for the undoped Fe3O4 films while a reduction in magnetoresistance and a departure from linear field dependence are observed for the Co-doped films.

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The dynamic response of nanoscale circular Permalloy antidot arrays in a square lattice geometry has been systematically investigated as a function of “hole” diameter using broadband ferromagnetic spectroscopy. Two main resonance modes were observed for the field applied along the lattice edge, whereas only a single main mode was observed along the diagonal of the square lattice. We also observed that the frequency of all modes can be systematically tuned by varying the antidot diameter. Our experimental results have been further validated using micromagnetic simulations.

We show that magnetic spin wave resonance modes in an antidot patterned array are sensitive to small changes in the magnetic configuration near dots, resulting in strong localization effects as the field is increased. Frequencies measured using ferromagnetic resonance from an antidot array patterned from a NiFe/IrMn bilayer are interpreted using micromagnetic calculations, and it is shown that the observed field dependence of the resonance response can be attributed to strong interdot localization of spin waves. This field tunable localization is created by stray fields produced by magnetic poles at the dot surfaces.

Exchange bias effects have been systematically investigated in nanoscale Cu ͑10 nm͒ / Ni 80 Fe 20 ͑30 nm͒ / Ir 75 Mn 25 ͑30 nm͒/Cu ͑2 nm͒ multilayer antidot arrays. The antidot arrays exhibit asymmetric and shifted hysteresis loops along the induced exchange bias direction, with higher coercivity and exchange bias field values as compared to a continuous film deposited under identical conditions. The evolution in exchange bias field with increasing antidot diameter is ascribed to the constraints imposed on the domain size in the Ir 75 Mn 25 layer and reduced ferromagnetic-ferromagnetic interactions in the Ni 80 Fe 20 layer.

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