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.

We explore the influence of the phase of localized plasmon resonances on the magneto-optical activity of nanoferromagnets. We demonstrate that these systems can be described as two orthogonal damped oscillators coupled by the spin-orbit interaction. We prove that only the spin-orbit induced transverse plasmon plays an active role on the magneto-optical properties by controlling the relative amplitude and phase lag between the two oscillators. Our theoretical predictions are fully confirmed by magneto-optical Kerr effect and optical extinction measurements in nanostructures of different size and shape.

A frontier topic in nanotechnology is the realization of multifunctional\ud nanoparticles (NPs) via the appropriate combination of different elements of\ud the periodic table. The coexistence of Fe and Ag in the same nanostructure, for\ud instance, is interesting for nanophotonics, nanomedicine, and catalysis. However,\ud alloying of Fe and Ag is inhibited for thermodynamic reasons. Here, we describe\ud the synthesis of Fe-doped Ag NPs via laser ablation in liquid solution, bypassing\ud thermodynamics constraints. These NPs have an innovative structure consisting\ud of a scaffold of face-centered cubic metal Ag alternating with disordered Ag–Fe\ud alloy domains, all arranged in a truffle-like morphology. The Fe–Ag NPs exhibit\ud the plasmonic properties of Ag and the magnetic response of Fe-containing\ud phases, and the surface of the Fe–Ag NPs can be functionalized in one step with\ud thiolated molecules. Taking advantage of the multiple properties of Fe–Ag NPs,\ud the magnetophoretic amplification of plasmonic properties is demonstrated with\ud proof-of-concept surface-enhanced Raman scattering and photothermal heating\ud experiments. The synthetic approach is of general applicability and virtually\ud permits the preparation of a large variety of multi-element NPs in one step