Plasmon-induced demagnetization and magnetic switching in nickel nanoparticle arrays

Abstract

We report on the manipulation of magnetization by femtosecond laser pulses in a periodic array of cylindrical nickel nanoparticles. By performing experiments at different wavelength, we show that the excitation of collective surface plasmon resonances triggers demagnetization in zero field or magnetic switching in a small perpendicular field. Both magnetic effects are explained by plasmon-induced heating of the nickel nanoparticles to their Curie temperature. Model calculations confirm the strong correlation between the excitation of surface plasmon modes and laser-induced changes in magnetization.Plasmonic nanostructures enable strong local enhancements of the optical field in areas that are substantially smaller than the wavelength of incident light. This capability offers prospects for magnetic recording. In heat-assisted magnetic recording (HAMR), a plasmonic near-field transducer (NFT) reduces the switching field of high-anisotropy materials via local heating. 1-3 The NFT in this application is a noble metal nanostructure that is placed near the recording medium. Excitation of the NFT at the plasmon resonance frequency efficiently transfers optical energy to a nanoscale region, enabling local switching at reduced magnetic field. In the realm of ultrafast all-optical switching (AOS), 4,5 the use of noble metal plasmonic antennas has also been considered. By placing gold antennas on top of a ferrimagnetic TbFeCo film, Liu and co-workers demonstrated the confinement of magnetic switching to sub-100 nm length scales. 6 .Independent from HAMR and AOS, a new discipline combining plasmonics and magnetism has emerged recently. 7,8 Experiments on pure ferromagnetic metals demonstrate that, despite stronger ohmic damping, they also support surface plasmon resonances. [9][10][11] This raises the question if one could nanostructure the magnetic medium itself to trigger magnetic switching via local enhancements of the optical field. To study the effect of plasmon resonances on magnetic switching it is advantageous to consider ferromagnetic nanoparticles of uniform size and shape. In such nanoparticles, plasmon resonances determine the magneto-optical activity via the excitation of two orthogonal electric dipoles. 12 Plasmon resonances in single ferromagnetic nanoparticles are rather broad. Yet, ordering of the particles into a periodic array significantly narrows the spectral response. 13 In this geometry, hybridization between localized surface plasmons and the diffracted orders of the array produces intense surface lattice resonances (SLRs). SLR modes a) sebastiaan.van.dijken@aalto.fi and, thereby, the optical, magneto-optical, and magnetic circular dichroism (MCD) properties of a ferromagnetic nanoparticle array can be tuned by changing the period or symmetry of the lattice 13-15 or the shape of the nanoparticles. 16 These versatile designer tools could thus be exploited to spectrally gauge the significance of the inverse Faraday effect and MCD on all-optical switching in ferromagnetic materials, a topic of intense sc...

Non-degenerate magneto-optical pump-probe spectroscopy of thermal and nonthermal spin dynamics in magnetic and magnetoplasmonic materials with sub-15 fs time resolution

“…For instance, Dürr and co-workers used plasmonic nanostructures to switch magnetization in TbFeCo films via plasmon-induced thermal effects 84 . Similar studies on plasmon-induced demagnetization processes were reported also by Kataja and co-workers on Ni nanoparticles arrays 85 , and by El-Ghazaly and colleagues in GdCo nanodots 86 . Fedyanin and collaborators have later demonstrated that thermal effects due to plasmon-driven electron-phonon scattering processes in nanoscale magnetoplasmonic crystals can drastically affect both the charge and spin dynamics with respect to a continuous film response 87 .…”

Non-degenerate magneto-optical pump-probe spectroscopy of thermal and nonthermal spin dynamics in magnetic and magnetoplasmonic materials with sub-15 fs time resolution

“…For instance, Dürr and co-workers used plasmonic nanostructures to switch magnetization in TbFeCo films via plasmon-induced thermal effects 84 . Similar studies on plasmon-induced demagnetization processes were reported also by Kataja and co-workers on Ni nanoparticles arrays 85 , and by El-Ghazaly and colleagues in GdCo nanodots 86 . Fedyanin and collaborators have later demonstrated that thermal effects due to plasmon-driven electron-phonon scattering processes in nanoscale magnetoplasmonic crystals can drastically affect both the charge and spin dynamics with respect to a continuous film response 87 .…”

Coupling phenomena and collective effects in resonant meta-atoms supporting both plasmonic and (opto-)magnetic functionalities: an overview on properties and applications [Invited]

“…The combination of plasmon-induced heating by light with ferromagnetic nanoislands enables one to overcome limitations imposed by the grain size. Studies in this direction were also reported by Kataja et al [168], who reported on the manipulation of magnetization by femtosecond laser pulses in a periodic array of cylindrical nickel nanoparticles. They showed a strong correlation between the excitation of SLRs and changes in magnetization.…”

Perspective: Strong microwave photon-magnon coupling in multiresonant dielectric antennas

“…However, this property turns to be useful for the control of the photon-magnon coupling with heat. The heat produced by light in the nanopatterned Pt layer is estimated to be comparable with that produced in nickel nanostructures (similar to Pt nickel is another poor plasmonic material 94 ), in which temperatures ∼ 350 o C were observed 95 .…”

Non-degenerate magneto-optical pump-probe spectroscopy of thermal and nonthermal spin dynamics in magnetic and magnetoplasmonic materials with sub-15 fs time resolution

“…For instance, Dürr and co-workers used plasmonic nanostructures to switch magnetization in TbFeCo films via plasmon-induced thermal effects 84 . Similar studies on plasmon-induced demagnetization processes were reported also by Kataja and co-workers on Ni nanoparticles arrays 85 , and by El-Ghazaly and colleagues in GdCo nanodots 86 . Fedyanin and collaborators have later demonstrated that thermal effects due to plasmon-driven electron-phonon scattering processes in nanoscale magnetoplasmonic crystals can drastically affect both the charge and spin dynamics with respect to a continuous film response 87 .…”

Coupling phenomena and collective effects in resonant meta-atoms supporting both plasmonic and (opto-)magnetic functionalities: an overview on properties and applications [Invited]

“…The combination of plasmon-induced heating by light with ferromagnetic nanoislands enables one to overcome limitations imposed by the grain size. Studies in this direction were also reported by Kataja et al [168], who reported on the manipulation of magnetization by femtosecond laser pulses in a periodic array of cylindrical nickel nanoparticles. They showed a strong correlation between the excitation of SLRs and changes in magnetization.…”

Perspective: Strong microwave photon-magnon coupling in multiresonant dielectric antennas

“…However, this property turns to be useful for the control of the photon-magnon coupling with heat. The heat produced by light in the nanopatterned Pt layer is estimated to be comparable with that produced in nickel nanostructures (similar to Pt nickel is another poor plasmonic material 94 ), in which temperatures ∼ 350 o C were observed 95 .…”

Non-degenerate magneto-optical pump-probe spectroscopy of thermal and nonthermal spin dynamics in magnetic and magnetoplasmonic materials with sub-15 fs time resolution

“…For instance, Dürr and co-workers used plasmonic nanostructures to switch magnetization in TbFeCo films via plasmon-induced thermal effects 84 . Similar studies on plasmon-induced demagnetization processes were reported also by Kataja and co-workers on Ni nanoparticles arrays 85 , and by El-Ghazaly and colleagues in GdCo nanodots 86 . Fedyanin and collaborators have later demonstrated that thermal effects due to plasmon-driven electron-phonon scattering processes in nanoscale magnetoplasmonic crystals can drastically affect both the charge and spin dynamics with respect to a continuous film response 87 .…”

Coupling phenomena and collective effects in resonant meta-atoms supporting both plasmonic and (opto-)magnetic functionalities: an overview on properties and applications [Invited]

“…The combination of plasmon-induced heating by light with ferromagnetic nanoislands enables one to overcome limitations imposed by the grain size. Studies in this direction were also reported by Kataja et al [168], who reported on the manipulation of magnetization by femtosecond laser pulses in a periodic array of cylindrical nickel nanoparticles. They showed a strong correlation between the excitation of SLRs and changes in magnetization.…”

Perspective: Strong microwave photon-magnon coupling in multiresonant dielectric antennas

“…However, this property turns to be useful for the control of the photon-magnon coupling with heat. The heat produced by light in the nanopatterned Pt layer is estimated to be comparable with that produced in nickel nanostructures (similar to Pt nickel is another poor plasmonic material 94 ), in which temperatures ∼ 350 o C were observed 95 .…”