Intertwined magnetooptical and plasmonic properties in magnetoplasmonic multilayers

Comunicación presentada en el 2nd Early Stage Researchers Workshop in Nanoscience, celebrado en Madrid el 28 y 29 de junio de 2012.This work deals with metal and metal-dielectric magnetoplasmonic (MP) multilayers, which combine noble metals and ferromagnetic ones and exhibit interrelated effects between the excitation of Surface Plasmon-Polaritons (SPPs) and their magnetooptical (MO) activity. We have studied the effect of the SPP resonances for the enhancement of the MO activity and the magnetic modulation of the SPP wavevector.Peer Reviewe

Optical and magneto-optical properties of highly distorted Fe 100 thin films

PACS:78.20.Ls,71.15.-m,75.50.BbTiN-capped epitaxial bcc Fe films exhibit strong changes in the out-of-plane interplanar distance depending on the growth conditions. At room temperature, the increase of the volume per Fe atom appears to be as large as 5%. The observed distortions deviate substantially from elastic behavior. We explain this effect as due to the presence of nitrogen incorporated into the Fe film during the capping layer deposition. In order to elucidate the effect that these distortions might have on the optical and magneto-optical properties, we study the diagonal and off-diagonal elements of the conductivity tensor for both distorted and undistorted structures. This is done by means of spectral ellipsometry and the Kerr effect in polar and transverse configurations in the energy range from 1.5 to 4.5 eV. Theoretical calculations using ab initio techniques for the observed structures are performed and compared with experimental data. Different possible mechanisms for the experimentally observed effects such as distortion, grain size, and orbital hybridization are studied and discussed.The work was carried out with financial support from the Spanish Commission of Science and Technology (Grant Nos. MAT98-0974-C03-01 and MAT99- 0724-C03-03) and Comunidad Auto´noma de Madrid (Grant No. 07N/0056/1999).Peer reviewe

From disk to ring: Aspect ratio control of the magnetoplasmonic response in Au/Co/Au nanostructures fabricated by hole-mask colloidal lithography

© 2015 AIP Publishing LLC. Morphology tuning of a series of Au/Co/Au nanostructures which gradually evolve from disk to ring allows controlling their optical and magneto-optical spectral responses in the visible and near infrared ranges. This is achieved by the combined use of hole mask colloidal lithography with off-normal deposition and substrate rotation. The morphological parameters responsible for this control, the disk/ring outer diameter and height, are determined by the off-normal deposition angle and the amount of deposited material, respectively. The single dipolar symmetric resonance mode in nanodisk splits into two characteristics, low (symmetric) and high energy (antisymmetric) ring modes. The ring's high energy mode, determined by the rings' section, is basically independent of the deposition angle, while the low energy symmetric mode is basically controlled by the outer diameter/height aspect ratio for both disk-like and ring structures, and therefore allowing a fine tuning of the wavelength position of this resonance.Funding from Spanish Ministry of Economy and Competitiveness through Grants “FUNCOAT” CONSOLIDER CSD2008–00023 and MAPS MAT2011–29194-C02–01are acknowledged. H. Y. Feng thanks the funding from CSC (Chinese Scholarship Council), Grant No. 201206220112. F. Luo would like to acknowledge the support of NSFC (Nos. 51002003 and 11090332) as well as Ramon y Cajal grant RYC-2012-11954.Peer Reviewe

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.We acknowledge financial support from MINECO through projects AMES (No. MAT 2014-58860-P), Quantum Spin Plasmonics (No. FIS2015-72035-EXP), and MIRRAS (No. MAT2017-84009-R) and Comunidad de Madrid (CM) through project SINOXPHOS-CM (No. S2018/BAA-4403). We acknowledge the service from the MiNa Laboratory at IMN and funding from MINECO under Project No. CSIC13-4E-1794 and from CM under Project No. S2013/ICE-2822 (Space-Tec), both with support from EU (FEDER, FSE). L.B., N.Z., and J.A. acknowledge support from the Department of Education, Research and Universities of the Basque Government through Project Ref. No. IT-1164-19, the Department of Industry of the Basque Government through Project No. KK-2018/00001, and the Spanish MICIN through Project Ref. No. PID2019-107432GB-I0

Capping layer effects in the structure and composition of Co nanoparticle ultrathin films

In this work, we present the correlation of the magnetic and structural properties of Co nanoparticles deposited by sputtering on Si3N4 substrates at different temperatures, and covered with different capping layers, two insulators, AlN and MgO, and a metal, Pt. High-resolution transmission electron microscopy shows the formation of CoPt3 and Co2N, for the Pt and AlN capping layers, respectively, giving to a significant change of the magnetic behavior. When using a cap of MgO, energy-filtered transmission electron microscopy shows an oxidized shell covering the Co nanoparticles with thickness decreasing as the deposition temperature increases, explaining the changes in the magnetic response induced by the MgO capping layer.This work has been funded by the Spanish Project No.MAT2002-04484-C03-02. Y.H. acknowledges the Consejo Superior de Investigaciones Científicas CSIC and Ramón y Cajal Program for financial support.Peer reviewe

Correlation between magnetic and transport properties in nanocrystalline Fe thin films: A grain-boundary magnetic disorder effect

We report on transport and magnetic measurements of islanded Fe(110) thin films. The electrical resistivity exhibits an anomalous increase at low temperatures, which disappears under the action of a magnetic field. Since such an anomaly completely disappears under the action of a magnetic field, it is inferred that it originates from spin-dependent scattering. We interpret the strong changes in the spin-dependent scattering in our films to be due to a low-temperature spin freezing of the island boundary magnetic regions that impedes ferromagnetic exchange between islands. A consequence of this magnetic behavior is the random arrangement of the individual magnetization, determined by the magnetocrystalline anisotropy of each island, resulting in an increase of the resistivity below the freezing temperature.Z.S. and J.L.M. acknowledge the Comunidad de Madrid for financial support. Work was performed under the financial support of the Comunidad de Madrid and the Spanish Commission of Science and Technology.Peer reviewe

Control of the perpendicular magnetic anisotropy of FePd films via Pd capping deposition

We have investigated the influence of two capping layers (MgO and Pd) on the magnetic anisotropy of highly anisotropic L10 FePd films. While we mainly found perpendicular magnetic anisotropy in MgO capped films, we observed that the Pd capping layer induces formation of an additional new phase near the FePd/Pd interface that exhibits in-plane magnetic anisotropy. The combined effect of these two anisotropies results in global canted magnetic anisotropy. Thus, our findings illustrate a mechanism to influence the magnetic anisotropy in FePd highly ordered alloys via adequate choice of capping layer materials.Peer reviewe

High magneto-optical activity and low optical losses in metal-dielectric Au/Co/Au-SiO2 magnetoplasmonic nanodisks

Póster presentado en la Conferencia Española de Nanofotónica (CEN2012), celebrada en Carmona (Sevilla) del 1 al 4 de octubre de 2012.Magnetoplasmonics deals with the study of systems where the plasmonic and magneto-optical (MO) properties coexist and show a distinct interaction between them. In this kind of systems, the plasmonic properties can become tunable upon application of a magnetic field, or the MO effects can be largely increased by plasmon resonance excitation, as a consequence of the enhancement of the electromagnetic (EM) field in the MO component of the structure. The study of the enhanced MO activity in structures with subwavelength dimensions is especially interesting since they may be viewed as nanoantennas in the visible range with MO functionalities. The light harvesting properties of these systems upon plasmon resonance excitation brings as a consequence an enhanced EM field in its interior, and more interestingly in the region where the MO active component is present. In fact, it has been recently demonstrated that the MO enhancement can be directly linked with the amount of EM field inside the MO layer, in such a way that this layer can be used as a probe to determine the EM field distribution inside a nanostructure.Therefore, optimizing the EM field distribution within the structure by maximizing it in the MO regions while simultaneously minimizing it in all the other, non MO active, lossy components, will allow for the development of novel systems with larger MO activity and reduced optical absorption, becoming an alternative to state of the art dielectric MO materials, like garnets. Here we will present our approach to face this problem, based on the insertion of a dielectric layer in Au/Co/Au magnetoplasmonic nanodisks. The resulting nanostructure consists of two metallic nanodisks coupled through the dielectric layer, with one of the nanodisk being purely Au and the other one Au/Co (see Figure 1(a)). This kind of systems presents two hybridized localized plasmon resonance modes, showing two peaks in both the extinction and the MO spectra (see Figure 1(b)). Moreover, the EM field inside the nanostructure is strongly redistributed, being strongly concentrated in the nanodisk composed only of pure noble metal (Figure 1(c)). By optimizing the internal architecture (position of the Co layer), a configuration where the system exhibits large MO activity and low optical extinction in the same wavelength range can be obtained, as it can be seen in the right side of Figure 1(b) for the high wavelength peak.Peer Reviewe

J.A.Schumpeter and Economic Sociology(6)

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