Josep Nogués

Publications (5)28.98 Total impact

• Source

  Available from: Paolo Vavassori

  Article: Polarizability and magnetoplasmonic properties of magnetic general nanoellipsoids.

  Nicolò Maccaferri, Juan B González-Díaz, Stefano Bonetti, Andreas Berger, Mikko Kataja, Sebastiaan van Dijken, Josep Nogués, Valentina Bonanni, Zhaleh Pirzadeh, Alexandre Dmitriev, Johan Akerman, Paolo Vavassori
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  ABSTRACT: An approach to compute the polarizability tensor of magnetic nanoparticles having general ellipsoidal shape is presented. We find a surprisingly excellent quantitative agreement between calculated and experimental magneto-optical spectra measured in the polar Kerr configuration from nickel nanodisks of large size (exceeding 100 nm) with circular and elliptical shape. In spite of its approximations and simplicity, the formalism presented here captures the essential physics of the interplay between magneto-optical activity and the plasmonic resonance of the individual particle. The results highlight the key role of the dynamic depolarization effects to account for the magneto-optical properties of plasmonic nanostructures.
  Optics Express 04/2013; 21(8):9875-89. · 3.59 Impact Factor
• Source

  Available from: Valentina Bonanni

  Article: Designer magnetoplasmonics with nickel nanoferromagnets.

  Valentina Bonanni, Stefano Bonetti, Tavakol Pakizeh, Zhaleh Pirzadeh, Jianing Chen, Josep Nogués, Paolo Vavassori, Rainer Hillenbrand, Johan Åkerman, Alexandre Dmitriev
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  ABSTRACT: We introduce a new perspective on magnetoplasmonics in nickel nanoferromagnets by exploiting the phase tunability of the optical polarizability due to localized surface plasmons and simultaneous magneto-optical activity. We demonstrate how the concerted action of nanoplasmonics and magnetization can manipulate the sign of rotation of the reflected light's polarization (i.e., to produce Kerr rotation reversal) in ferromagnetic nanomaterials and, further, how this effect can be dynamically controlled and employed to devise conceptually new schemes for biochemosensing.
  Nano Letters 12/2011; 11(12):5333-8. · 13.20 Impact Factor
• Source

  Available from: Paolo Vavassori

  Article: Plasmonic Nickel Nanoantennas.

  Jianing Chen, Pablo Albella, Zhaleh Pirzadeh, Pablo Alonso-González, Florian Huth, Stefano Bonetti, Valentina Bonanni, Johan Akerman, Josep Nogués, Paolo Vavassori, Alexandre Dmitriev, Javier Aizpurua, Rainer Hillenbrand
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  ABSTRACT: The fundamental optical properties of pure nickel nanostructures are studied by far-field extinction spectroscopy and optical near-field microscopy, providing direct experimental evidence of the existence of particle plasmon resonances predicted by theory. Experimental and calculated near-field maps allow for unambiguous identification of dipolar plasmon modes. By comparing calculated near-field and far-field spectra, dramatic shifts are found between the near-field and far-field plasmon resonances, which are much stronger than in gold nanoantennas. Based on a simple damped harmonic oscillator model to describe plasmonic resonances, it is possible to explain these shifts as due to plasmon damping.
  Small 06/2011; · 8.35 Impact Factor
• Source

  Available from: Randy Kenneth Dumas

  Article: First-order reversal curve analysis of graded anisotropy FePtCu films

  Valentina Bonanni, Yeyu Fang, Randy K. Dumas, Chaolin Zha, Stefano Bonetti, Josep Nogués, Johan Åkerman
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  ABSTRACT: The reversal mechanisms of graded anisotropy FePtCu films have been investigated by alternating gradient magnetometer (AGM) and magneto-optical Kerr effect (MOKE) measurements with first-order reversal curve (FORC) techniques. The AGM-FORC analysis, which clearly shows the presence of soft and hard components, is unable to resolve how these phases are distributed throughout the film thickness. MOKE-FORC measurements, which preferentially probe the surface of the film, reveal that the soft components are indeed located toward the top surface. Combining AGM-FORC with the inherent surface sensitivity of MOKE-FORC analysis allows for a comprehensive analysis of heterogeneous systems such as graded materials.
  Applied Physics Letters 11/2010; 97(20):202501-202501-3. · 3.84 Impact Factor
• Article: Probing vertically graded anisotropy in FePtCu films

  Randy K. Dumas, Yeyu Fang, B. J. Kirby, Chaolin Zha, Valentina Bonanni, Josep Nogués, Johan Åkerman
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  ABSTRACT: Field-dependent polarized neutron reflectivity (PNR) and magnetometry are employed to study the magnetic properties of compositionally uniform and graded FePtCu films as a function of annealing temperature (TA). The PNR results are able to directly probe the compositional and anisotropy variations through the film thickness. Further details about how the reversal mechanisms evolve are then elucidated by using a first-order reversal curve technique. The reversal of the graded sample annealed at 300 °C occurs by an initial rapid switching of the dominant soft A1 phase toward the surface of the film, followed by the gradual reversal of the residual hard phase components toward the bottom. This indicates that the anisotropy gradient is not well established at this low TA. A fundamentally different mechanism is found after annealing at 400 °C, where the rapid switching of the entire film is preceded by a gradual reversal of the soft layers. This suggests that the anisotropy gradient has become better established through the film thickness. The field-dependent PNR measurements confirm the existence of an anisotropy gradient, where the lower (higher) anisotropy portions are now toward the bottom (top) of the film because of the Cu compositional gradient. However, after annealing at 500 °C, a single rapid reversal is found, indicating the formation of a uniform hard film. In this case, PNR demonstrates a more uniform magnetic depth profile that is consistent with a uniform reference sample, suggesting significant interdiffusion of the Cu is degrading the compositional and induced anisotropy gradient at this elevated TA.
  Phys. Rev. B. 84(5).