A novel vibrational spectroscopy using spintronic-plasmonic antennas: Magneto-refractive surface-enhanced infrared absorption

We present experimental and theoretical results of the molecular sensing performance of a novel platform based on magnetic modulation of surface-enhanced infrared absorption spectroscopy. For this, we study the effect that molecular infrared vibrations of a PMMA layer have on the optical and magneto-refractive response of spintronic antennas. Specifically, a periodic array of rods is fabricated from giant-magneto-resistance Au/Ni81Fe19 metallic multilayers, and the effect of depositing a layer of PMMA on top of the array is investigated from both experimental and theoretical points of view. We find that the relative changes induced by the infrared vibrations of PMMA on the magneto-refractive signal are larger than the relative changes induced on the optical transmission. This result indicates that the magneto-refractive response is more sensitive to the excitation of molecular vibrations than the optical response and fosters the development of a novel type of an infrared sensing technique based on spintronic antennas: Magneto-Refractive Surface-Enhanced Infrared Absorption (SEIRA) Spectroscopy.