Tuning the Magneto-Optical Response of Nanosize Ferromagnetic Ni Disks Using the Phase of Localized Plasmons

CFM Seminars

Paolo Vavassori (CIC nanoGUNE)
Auditorium of the Centro de Fisica de Materiales, Paseo Manuel de Lardizabal 5, Donostia-San Sebastián
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Tuning the Magneto-Optical Response of Nanosize Ferromagnetic Ni Disks Using the Phase of Localized Plasmons ** ** ** ** ** ** **Tuning the Magneto-Optical Response of Nanosize Ferromagnetic Ni Disks Using** **the Phase of Localized Plasmons** _P. Vavassori*_ 1,2 _, N. Maccaferri_ 1 _, V. Bonanni_ 3 _, S. Bonetti_ 4 _, Z. Pirzadeh_ 5 _,_ _A. Dmitriev_ 5 _, K. Lodewijks_ 5 _,_ _J. Nogués_ 6 _, M. Kataja_ 7 _, S._ _Van Dijken_ 7 _, and J. Akerman_ 8 __ (1) CIC Nanogune, San Sebastian, Spain (2) Ikerbasque, Basque Foundation for Science, Bilbao, Spain (3) CNR-ISTM and INSTM, 20133 Milano, Italy (4) Department of Physics, Stanford University and Stanford Institute for Materials and Energy Science (SIMES), SLAC National Accelerator Laboratory, CA 94305–2004 Stanford, U.S.A. (5) Applied Physics, Chalmers University of Technology, Göteborg, Sweden (6) ICREA and Catalan Institute of Nanotechnology, Bellaterra, Spain (7) Applied Physics, Aalto University, Espoo, Finland (8) Materials Physics, Royal Institute of Technology, Kista, Sweden *E-mail: p.vavassori@nanogune.eu Magneto-plasmonics materials combine magnetic and plasmonic functionalities and are an emerging field of intense research as they would allow the design of a new class of magnetically controllable optical nano-devices. Magneto- plasmonics studies have mainly focused on hybrid multilayered structures consisting of noble metals and ferromagnetic materials, where the noble metal increases the plasmon response of the ferromagnetic material. Plasmon properties of pure ferromagnetic nanostructures are a widely unexplored terrain, although they offer the advantage of stronger magnetic polarization and less demanding fabrication. Here we explore the opportunities arising from direct excitation of localized surface plasmons (LSPs) in purely ferromagnetic nanostructures due to the intertwined optical and magneto-optical properties. We first show, using optical near-field microscopy and far-field spectroscopy, that pure ferromagnetic nanostructures support LSP resonances as predicted by theory [1]. A special feature of the ferromagnetic nanostructures is that the near and far-field spectra are strongly shifted against each other, which can be assigned to the their higher plasmon damping, when compared to noble metals. We then investigate the spectral magneto-optical (MO) response of such nanostructures using different Kerr effect configurations [2-4]. We extended present theoretical models based on generalized ellipsoidal nanoparticles in order to account for both plasmonic and MO effects [4]. Guided by these experimental findings and the results of our modeling efforts, we combine the excitation of LSPs together with polarizability anisotropy to tune the phase difference between the optical and MO induced polarizabilities beyond what is offered by constituent material intrinsic properties and to manipulate the reflected light’s polarization [3]. Such magneto-plasmonic nanostructures could be a building block for future biotechnological and optoelectronic applications In particular we show that magnetoplasmonic nanoparticles based detection schemes allow for unprecedented sensitive detection. **_References_** [1] J. Chen et al., _Small_ **7** , 2341 (2011) [2] V. Bonanni et al., _Nano Lett._ **11** , 5333 (2011) [3] N. Maccaferri et al., _Phys. Rev. Lett._ **111** , 5333 (2013) [4] K. Lodewijks et al., submitted to _Nano Lett._ [5] N. Maccaferri et al., _Opt. Express_ **21** , 9875 (2013) [6] N. Maccaferri et al., submitted to _Physica Status Solidi_ [7] N. Maccaferri et al., in preparation.