Intertwine magnetooptical and plasmonic properties in metal and metal/dielectric magnetoplasmonic multilayers

This thesis 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. Moreover, these MP systems have been used as transducers in sensing applications

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

Strain-induced enhancement of the thermoelectric power in thin films of hole-doped La2NiO4+δ

We propose a novel route for optimizing the thermoelectric power of a polaronic conductor, independent of its electronic conductivity. This mechanism is exemplified here in thin-films of La2NiO4+δ. Tensile stress induced by epitaxial growth on SrTiO3 doubles the thermoelectric power of ≈15 nm thick films relative to ≈90 nm films, while the electronic conductivity remains practically unchanged. Epitaxial strain influences the statistical contribution to the high temperature thermopower, but introduces a smaller correction to the electronic conductivity. This mechanism provides a new way for optimizing the high temperature thermoelectric performance of polaronic conductorsThis work was supported by the European Research Council (ERC StG-259082, 2DTHERMS), and Ministerio de Economía y Competitividad of Spain through the project MAT2010-16157, and a Ph.D. grant of the FPI program (J.M.V.-F.)S

Analysis of the temperature dependence of the thermal conductivity of insulating single crystal oxides

The temperature dependence of the thermal conductivity of 27 different single crystal oxides is reported from ≈20 K to 350 K. These crystals have been selected among the most common substrates for growing epitaxial thin-film oxides, spanning over a range of lattice parameters from ≈3.7 Å to ≈12.5 Å. Different contributions to the phonon relaxation time are discussed on the basis of the Debye model. This work provides a database for the selection of appropriate substrates for thin-film growth according to their desired thermal properties, for applications in which heat management is importantThis work was supported by the European Research Council (Grant No. ERC StG-259082, 2DTHERMS), and MINECO of Spain (Project No. MAT2013-44673-R) and Xunta de Galicia (Project No. EM2013/037). V.P. acknowledges support from the Ramon y Cajal Program (No. RYC-2011-09024) and E.F.V. from Xunta de Galicia through the I2C planS

Magneto-optic enhancement and magnetic properties in Fe antidot films with hexagonal symmetry

The magneto-optic and magnetic properties of hexagonal arrays of holes in optically thin iron films are presented. We analyze their dependence on the hole radius and compare the results to a continuous iron film of the same thickness. We observe a large enhancement of the magneto-optic Kerr rotation with respect to that of the continuous film, at frequencies where surface-plasmon excitations are expected. The spectral position of the Kerr maxima can be tuned by the size and the distance between the holes. Additional simulations are in very good agreement with the experiment and thus confirm the effect of the surface plasmons on the Kerr rotation. The altering of the magnetic properties by the hole array is also visible in the hysteretic behavior of the sample where a significant hardening is observed.E.Th.P. acknowledges the financial support from the Icelandic Science Foundation and the Swedish Foundation for International Cooperation in Research and Higher Education STINT . M.G. thanks the Helmholtz-Zentrum Berlin for financial support. A.G.-M. and E. F.-V. acknowledge financial support from the EU under Project No. NMP3-SL-2008-214107-Nanomagma and from the Spanish MICINN (Consolider 2010 References No. CSD2008-00023-Funcoat and No. MAT2008-06765-C02-01/NAN . E.F.-V also acknowledges financial support from the CSIC via the JAE-Pre program. The authors acknowledge also the Knut and AliceWallenberg Foundation.Peer reviewe

Plasmonic and magnetoplasmonic nanostructures characterized by Scanning Near-field Optical Microscopy

Comunicación y presentación a Fuerzas y Tunel 2010.Most plasmonic devices are passive devices since their electromagnetic properties depend mainly on fixed properties such as the shape of the structures, their constitutive materials, and the dielectric media. A way to turn plasmonic devices into active ones is to use ferromagnetic metals, since due to their magneto-optical (MO) activity the optical response when applying an external low magnetic field can be modified. Unfortunately, plasmon resonances are critically broadened in ferromagnetic materials due to their important electromagnetic losses. An alternative is to combine ferromagnetic materials with noble metals. Recently, we have demonstrated that Au/Co/Au nanodisks exhibit enhanced magnetoplasmonic properties such as a significant increase of the MO activity when the localized surface plasmon (LSP) resonance is excited [1,2].Peer reviewe

Apparent auxetic to non-auxetic crossover driven by Co2+ redistribution in CoFe2O4 thin films

Oxide spinels of general formula AB2O4 (A = Mg2+, Fe2+; B = Al3+, Cr3+, etc.) constitute one of the most abundant crystalline structures in mineralogy. In this structure, cations distribute among octahedral and tetrahedral sites, according to their size and the crystal-field stabilization energy. The cationic arrangement determines the mechanical, magnetic, and transport properties of the spinel and can be influenced by external parameters like temperature, pressure, or epitaxial stress in the case of thin films. Here, we report a progressive change in the sign of the Poisson ratio, ν, in thin films of CoFe2O4, defining a smooth crossover from auxetic (ν 0) behavior in response to epitaxial stress and temperature. Microstructural and magnetization studies, as well as ab initio calculations, demonstrate that such unusual elastic response is actually due to a progressive redistribution of Co2+ among the octahedral and tetrahedral sites of the spinel structure. The results presented in this work clarify a long standing controversy about the magnetic and elastic properties of Co-ferrites and are of general applicability for understanding the stress-relaxation mechanism in complex crystalline structures.This work has received financial support from Ministerio de Economía y Competitividad (Spain) under Project No. MAT2016-80762-R and MAT2017-82970-C2-R, Xunta de Galicia (Centro singular de investigación de Galicia accreditation 2016-2019, No. ED431G/09), the European Union (European Regional Development Fund-ERDF), and the European Commission through the Horizon H2020 funding by H2020-MSCA-RISE-2016-Project No. 734187–SPICOLOST. I.L.d.P. and B.R.-M. thank the funding under the ESTEEM2 project and the researchers L.A. Rodríguez and E. Snoeck for preliminary Lorentz Microscopy (L.M.) and electron holography (EH) studies in CoFe2O4 samples synthesized by PAD method performed at CEMES (Toulouse)S

Enhanced gas sensing performance of TiO2 functionalized magneto-optical SPR sensors

9 páginas, 7 figurasPorous TiO2 thin films deposited by glancing angle deposition are used as sensing layers to monitor their sensing capabilities towards Volatile Organic Compounds both in a standard Surface Plasmon Resonance (SPR) sensor and in Magneto-Optical Surface Plasmon Resonance (MO-SPR) configuration in order to compare their sensing performances. Here our results on the enhanced sensing capability of these TiO2 functionalized MO-SPR sensors with Au/Co/Au transducers with respect to traditional SPR gas sensors are presented.This work has been funded by the European Commission (NMP3-SL-2008-214107-Nanomagma), the Spanish MICINN (CSD 2008-00023, MAT 2008-06765-C02-01/NAN, MAT2010-21228), CSIC (JAE fellowship for E. F.-V.) and Comunidad de Madrid (S2009 / MAT – 1726, S2009/TIC – 1476).Peer reviewe

Magnetoplasmonics: Combining Magnetic and Plasmonic Functionalities

Comunicación presentada en el 3rd European Workshop on Self Organized Nanomagnets, celebrado en Guadarrama del 16 al 20 de abril de 2012.Nanosystems with combined magnetic and plasmonic functionalities have in recent years become an active topic of research. In these new stn-lctures, know as magneto-plasmonics, magnetic and plasmonic properties are interlwined, allowing for example plasmonic properties to become tunable upon de application of a magnetic field (active plasmonics), or the Magneto*Optical (MO) effects to be largely increased by plasmon resonance excitation, as a consequence of the enhancement of the electromagnetic (EM) field in the MO active component of the structure. ln this last case, 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 bring as a consequence an enhanced EM field in its interior, and more interestingly in the region where the MO active component is present. At this stage, optimizing the EM field distribution within the structure by maximizing it in the MO components region while simultaneously minimizingit in all the other, non MO active, lossy components, will allow for the development of novel systems with even larger MO activity with reduced optical losses .Peer Reviewe

Optimizing light harvesting for high magneto-optical performance in metal and metal-dielectric magnetoplasmonic nanodiscs

Póster presentado en Nanolight, celebrado en Benasque (España).Magnetoplasmonics deals with the study of materials and/or phenomena involving both plasmonic and magneto-optical (MO) properties. A two-way path connects both properties: the MO response of the system can be modified by the presence of plasmon resonances and the plasmons properties can be modulated by means of an applied magnetic field. Here we focus on the first path, in particular on the MO activity enhancement in nano-discs due to the excitation of localized surface plasmons (LSP).EU (NMP3-SL-2008-214107-Nanomagma), Spanish Ministry (“FUNCOAT” CONSOLIDER INGENIO 2010 CSD2008-00023, MAGPLAS MAT2008-06765-C02-01/NAN, PLASMAR MAT2010-10123-E, and MAPS MAT2011-29194-C02-01), Comunidad de Madrid (“NANOBIOMAGNET”, S2009/MAT-1726 and >MICROSERES-CM”, S2009/TIC-1476), and CSIC/FSE (JAE-Doc fellowship for D. Meneses-Rodríguez, and JAE-Predoc fellowship for E. Ferreiro-Vila).Peer Reviewe