Magnetic polarization in the optical absorption of metallic nanoparticles

11 pags, 4 figs. -- OCIS codes: (250.5403) Plasmonics; (240.6680) Surface plasmons; (290.4020) Mie theoryWe find remarkably strong absorption due to magnetic polarization in common colloidal and lithographic metallic nanoparticles. Our analysis is based upon a thorough examination of the dipolar electric and magnetic polarizabilities for representative combinations of nanoparticle composition, size, and morphology. We illustrate this concept by first discussing absorption in metallic spheres and then exploring ellipsoids, disks, and rings. Magnetic polarization reaches ∼ 90% of the total absorption in 100 nm disks and rings for wavelengths above 1 μ m under co-linear electric and magnetic irradiation. Our results demonstrate that the magnetic contribution to absorption cannot be naively overlooked, as it can largely exceed the contribution of electric polarization © 2012 Optical Society of America.This work has been supported in part by the Spanish MICINN (MAT2010-14885 and Consolider NanoLight.es) and the European Commission (FP7-ICT-2009-4-248909-LIMA and FP7ICT-2009-4-248855-N4E). A.A.-G. and A. M. acknowledge financial support through FPU from the Spanish ME. V. M. acknowledges a CSIC - JAE grant