Magnetic hot spots in closely spaced thick gold nanorings

María Lorente Crespo, Li Wang, Ruben Ortuno, Carlos Garcia-Meca, Yasin Ekinci, Alejandro Martinez*

*Corresponding author for this work

Research output: Contribution to journalArticle

50 Citations (Scopus)


Light-matter interaction at optical frequencies is mostly mediated by the electric component of the electromagnetic field, with the magnetic component usually being considered negligible. Recently, it has been shown that properly engineered metallic nanostructures can provide a magnetic response at optical frequencies originated from real or virtual flows of electric current in the structure. In this work, we demonstrate a magnetic plasmonic mode which emerges in closely spaced thick gold nanorings. The plasmonic resonance obtains a magnetic dipole character by sufficiently increasing the height of the nanorings. Numerical simulations show that a virtual current loop appears at resonance for sufficiently thick nanorings, resulting in a strong concentration of the magnetic field in the gap region (magnetic hot spot). We find that there is an optimum thickness that provides the maximum magnetic intensity enhancement (over 200-fold enhancement) and give an explanation of this observation. This strong magnetic resonance, observed both experimentally and theoretically, can be used to build new metamaterials and resonant loop nanoantennas at optical frequencies.

Original languageEnglish
Pages (from-to)2654-2661
Number of pages8
JournalNano Letters
Issue number6
Publication statusPublished - Jun 2013


  • Surface plasmons
  • plasmonic array
  • gold nanorings
  • optical magnetism
  • magnetic field enhancement
  • nanoantennas


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