Department of Applied Physics


We design plasmonic excitations in magnetic metamaterials to tailor their magneto-optical response, realize magnetic-field control of plasmonic lasing, and enhance the efficiency of all-optical magnetic switching.

The integration of plasmonics and magneto-optics has led to the emergence of a new research field known as magnetoplasmonics. The goal of magnetoplasmonic is twofold. First, the integration of magnetic materials with plasmonic structures enables active light manipulation at the nanoscale and field-controlled breaking of time-reversal symmetry. Second, the excitation of surface plasmons in magnetic materials can be used to resonantly enhance and spectrally tailor their magneto-optical response [1-3]. We study magnetoplasmonic effects in ferromagnetic and ferrimagnetic metamaterials as well as magnetic/noble metal hybrids. Our plasmonic nanostructures are patterned by electron-beam lithography.

We have demonstrated strong resonant enhancements of the magneto-optical activity by exciting collective surface lattice resonances (SLRs) in periodic ferromagnetic nanodisk arrays [5,8]. In subsequent studies, we further tailored the magneto-optical response by the integration of noble metals. For instance, we investigated arrays in which Ni and Au nanodisks are ordered in a checkerboard pattern [7], arrays made of Ni/SiO2/Au dimers [12], and arrays of Ni or Co/Pt multilayer nanodisks patterned on top of a continuous Au/SiO2 film [13,15]. In these hybrid metamaterials, the excitation of collective plasmon resonances enhances the magneto-optical activity by more than an order of magnitude. This effect together with the spectral specificity of the magneto-optical response could be used for high-resolution refractive index sensing in biomedical applications [4,10].

Plasmonic lasing
Illsutration of magnetic-field control of plasmonic lasing in an array of Co/Pt multilayer nanodisks on top of a Au/SiO2 film. Image by Jenna Rantala.

We are working on plasmonic lasing in ferromagnetic nanodisk arrays overlaid with organic gain media. In an initial study, we demonstrated lasing in Ni nanodisk arrays patterned onto a glass substrate [11]. More recently, we realized full on/off switching of plasmonic lasing in a hybrid magnetoplasmonic system with perpendicularly magnetized Co/Pt nanodisk arrays on top of a continuous Au/SiO2 film [16]. The strong response of plasmonic lasing to an external magnetic field in this metamaterial is explained by the formation of chiral plasmonic modes caused by time-reversal symmetry breaking in the magnetic nanodisks. While the splitting of the chiral modes is only about 0.5 nm, its effect on light emission is greatly enhanced in the nonlinear lasing regime. This groundbreaking finding has important implications for studies on topological photonics.

We are also studying how plasmon excitations improve the efficiency of single-pulse all-optical switching in ferrimagnetic nanodisk arrays. Materials that we consider include CoFeGd alloys and Pt/Gd/Co multilayers. Experiments indicate that surface lattice resonances do reduce the switching energy by up to a factor five, while even larger gains are attained in the magneto-optical readout of the magnetization state. In another project, we leverage the effective magnetic field of surface plasmon polaritons to manipulate magnetic domain walls or trigger magnetization dynamics.


1. N. Maccaferri, J.B. Gonzalez-Diaz, S. Bonetti, A. Berger, M. Kataja, S. van Dijken, J. Nogues, V. Bonanni, Z. Pirzadeh, A. Dmitriev, J. Åkerman, P. Vavassori. Polarizability and magnetoplasmonic properties of magnetic general nanoellipsoids. Optics Express 21, 9875 (2013).

2. N. Maccaferri, A. Berger, S. Bonetti, V. Bonanni, M. Kataja, Q.H. Qin, S. van Dijken, Z. Pirzadeh, A. Dmitriev, J. Nogues, J. Åkerman, P. Vavassori. Tuning the magneto-optical response of nanosize ferromagnetic Ni disks using the phase of localized plasmons. Physical Review Letters 111, 167401 (2013).

3. N. Maccaferri, M. Kataja, V. Bonanni, S. Bonetti, Z. Pirzadeh, A. Dmitriev, S. van Dijken, J. Åkerman, P. Vavassori. Effects of a non-absorbing substrate on the magneto-optical Kerr response of plasmonic ferromagnetic nanodisks. Physica Status Solidi A 211, 1067 (2014).

4. N. Maccaferri, K.E. Gregorczyk, T.V.A.G. Oliveira, M. Kataja, S. van Dijken, Z. Pirzadeh, A. Dmitriev, J. Åkerman, M. Knez, P. Vavassori. Ultrasensitive and label-free molecular-level detection enabled by light phase control in magnetoplasmonic nanoantennas. Nature Communications 6, 6150 (2015).

5. M. Kataja, T.K. Hakala, A. Julku, M.J. Huttunen, S. van Dijken, P. Törmä. Surface lattice resonances and magneto-optical response in magnetic nanoparticle arrays. Nature Communications 6, 7072 (2015).

6. M. Kataja, S. Pourjamal, S. van Dijken. Magnetic circular dichroism of non-local surface lattice resonances in magnetic nanoparticle arrays. Optics Express 24, 3562, (2016).

7. M. Kataja, S. Pourjamal, N. Maccaferri, P. Vavassori, T.K. Hakala, M.J. Huttunen, P. Törmä, S. van Dijken. Hybrid plasmonic lattices with tunable magneto-optical activity. Optics Express 24, 3652 (2016).

8. N. Maccaferri, L. Bergamini, L M. Pancaldi, M.K. Schmidt, M. Kataja, S. van Dijken, N. Zabala, J. Aizpurua, P. Vavassori.  Anisotropic nanoantenna-based magnetoplasmonic crystals for highly enhanced and tunable magneto-optical activity. Nano Letters 16, 2533 (2016).

9. M. Kataja, F. Freire-Fernández, J.P. Witteveen, T.K. Hakala, P. Törmä, S. van Dijken. Plasmon-induced demagnetization and magnetic switching in nickel nanoparticle arrays. Applied Physics Letters 112, 072406 (2018).

10. S. Pourjamal, M. Kataja, N. Maccaferri, P. Vavassori, S. van Dijken. Hybrid Ni/SiO2/Au dimer arrays for high-resolution refractive index sensing. Nanophotonics 7, 905 (2018).

11. S. Pourjamal, T.K. Hakala, M. Nečeda, F. Freire-Fernández, M. Kataja, H. Rekola, J.P. Martikainen, P. Törmä, S. van Dijken. Lasing in Ni nanodisk arrays. ACS Nano 13, 5686 (2019).

12. S. Pourjamal, M. Kataja, N. Maccaferri, P. Vavassori, S. van Dijken. Tunable magnetoplasmonics in lattices of Ni/SiO2/Au dimers. Scientific Reports 9, 9907 (2019).

13. F. Freire-Fernández, M. Kataja, S. van Dijken. Surface-plasmon-polariton-driven narrow-linewidth magneto-optics in Ni nanodisk arrays. Nanophotonics 9, 113 (2020).

14. A.N. Kuzmichev, D.A. Sylgacheva, M.A. Kozhaev, D.M. Krichevsky, A.N. Shaposhnikov, V.N. Berzhansky, F. Freire-Fernández, H.J. Qin, O.E. Popova, N. Keller, S. van Dijken, A.I. Chernov, V.I. Belotelov. Influence of the plasmonic nanodisk positions inside a magnetic medium on the Faraday effect enhancement. Physica Status Solidi – Rapid Research Letters 14, 1900682 (2020).

15. F. Freire-Fernández, R. Mansell, S. van Dijken. Magnetoplasmonic properties of perpendicularly magnetized [Co/Pt]N nanodots. Physical Review B 101, 054416 (2020).

16. F. Freire-Fernández, J. Cuerda, K.S. Daskalakis, S. Perumbilavil, J.-P. Martikainen, K. Arjas, P. Törmä, S. van Dijken. Magnetic on–off switching of a plasmonic laser. Nature Photonics 16, 27 (2022).

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