Room Temperature In-plane <100> Magnetic Easy Axis for Fe3O4/SrTiO3(001):Nb Grown by Infrared PLD

We examine the magnetic easy-axis directions of stoichiometric magnetite films grown on SrTiO3:Nb by infrared pulsed-laser deposition. Spin-polarized low-energy electron microscopy reveals that the individual magnetic domains are magnetized along the in-plane film directions. Magneto-optical Kerr effect measurements show that the maxima of the remanence and coercivity are also along in-plane film directions. This easy-axis orientation differs from bulk magnetite and films prepared by other techniques, establishing that the magnetic anisotropy can be tuned by film growth.Comment: 3 pages, 3 figure

Mössbauer and Magnetic Properties of Coherently Mixed Magnetite-Cobalt Ferrite Grown by Infrared Pulsed-Laser Deposition

We have studied the magnetic properties and the composition of cobalt ferrite single crystal films on SrTiO3 : Nb grown by infrared pulsed-laser deposition. Mössbauer spectra have been recorded from both the target used to grow the films and the films themselves. The Mössbauer spectra of the target taken at low temperatures show a strong dependence of the recoil free fraction of the octahedral sites with temperature. The films composition, with a coexistence of Co-enriched cobalt ferrite and magnetite, has been estimated assuming a similar ratio of the recoil free fractions of the films. X-ray absorption and x-ray magnetic circular dichroism measurements confirm the valence composition of the film and show ferromagnetic Fe-Co coupling in the films with a coercive field around 0.5 T at room temperature. The combination of these characterization techniques allows establishing the coherent structural and magnetic properties of this biphase system

Análisis por espectroscopias láser de yesería policromada

8 pags., 8 figs., 1 tab.Peer reviewe

UV laser removal of varnish on tempera paints with nanosecond and femtosecond pulses

Two laser cleaning approaches based on ablation by ultraviolet laser pulses of femtosecond (fs) and nanosecond (ns) durations for the removal of shellac varnish from egg-yolk based tempera paints are investigated. Laser irradiation effects, induced on the varnish layer and on the underlying temperas by multiple pulses in the fs domain at 398 and 265 nm and single pulses in the ns domain at 213 nm, were examined following a spectroanalytical approach. By using optical microscopy, colorimetry and laser induced fluorescence it was found that irradiation of the varnished temperas with fs pulses changes the texture of the varnish surface and results in degradation of the underlying coloured paint. In contrast, operating with pulses of 15 ns at the highly absorbed wavelength of 213 nm, controlled micrometric layer removal of the varnish is possible without noticeable modification of the coloured temperas. These results widen the choice of laser conditions for painting restoration

Reflectance Spectroscopy as a Novel Tool for Thickness Measurements of Paint Layers

A major challenge in heritage science is the non-invasive cross-sectional analysis of paintings. When low-energy probes are used, the presence of opaque media can significantly hinder the penetration of incident radiation, as well as the collection of the backscattered signal. Currently, no technique is capable of uniquely and noninvasively measuring the micrometric thickness of heterogeneous materials, such as pictorial layers, for any painting material. The aim of this work was to explore the possibility of extracting stratigraphic information from reflectance spectra obtained by diffuse reflectance spectroscopy (DRS). We tested the proposed approach on single layers of ten pure acrylic paints. The chemical composition of each paint was first characterised by micro-Raman and laser-induced breakdown spectroscopies. The spectral behaviour was analysed by both Fibre Optics Reflectance Spectroscopy (FORS) and Vis-NIR multispectral reflectance imaging. We showed that there is a clear correlation between the spectral response of acrylic paint layers and their micrometric thickness, which was previously measured by Optical Coherence Tomography (OCT). Based on significant spectral features, exponential functions of reflectance vs. thickness were obtained for each paint, which can be used as calibration curves for thickness measurements. To the best of our knowledge, similar approaches for cross-sectional measurements of paint layers have never been tested

Dataset for the paper “Martínez-Weinbaum, M.; Lozano-Carbó, M.; Maestro-Guijarro, L.; Carmona-Quiroga, P.M.; Oujja, M.; Castillejo, M., Comparison of the Use of Traditional Solvents and Nanosecond 213 nm Nd:YAG Laser in Thinning Naturally Aged Varnish on a Contemporary Oil Easel Painting. Heritage. 2023, 6(2), 957-967.”

The study was undertaken in a contemporary oil easel painting which was temporarily loaned from the Restoration-Conservation Laboratory of the Faculty of Fine Arts of the University of Barcelona. Different varnish removal procedures were assessed over this painting, and, in order to analyse and compare the efficiency of the methods, several non-invasive and invasive techniques were applied. This dataset consists of images of the artwork (general and detail) and the results of the different cleaning procedures; the varnish removal test conditions performed; Laser-induced Breakdown Spectroscopy (LIBS) spectra; Laser-induced Fluorescence (LIF) spectra; and Fourier-transform infrared spectroscopy (FTIR Spectroscopy). This information allows for assessing the results achieved with each cleaning methodology. Images are presented in JPG format. All spectra are presented in CSV format, on a single page. Descriptions of the selected areas and the experimental conditions in which the spectra were taken and the name of the column values are included at the top of each page. To illustrate the artwork, we took one image of the painting considered in the study (Fig. 1) and a general image under UV light of the picture (Fig. 2). Additionally, we can see the outcomes of varnish removal in the detail photos digital microscopy images (Fig. 3), and in detail UV light photograph of one of the cleaned areas (Fig. 4). For kinetic LIBS, 1 file per each uncleaned and cleaned by different methods area is included. Each file is composed of 41 columns, the first one (x) for wavelength and, the other 40 (y) for intensity. For LIF, 1 file per sample of the analysis of the fluorescence of each un/cleaned area. Each file is composed of 2 columns (wavelength and intensity). For FTIR, 1 file for the characterisation of the varnish, which is composed of 2 columns, the first one indicates the wavenumber (x), and the second one the transmittance (y).[EN] The removal of aged varnish on artistic paintings is a delicate intervention and the use of UV laser for this purpose is of special relevance. In particular, the use of nanosecond-pulsed lasers operating at 213 nm has been noted to produce good results in mock-up samples, but it has not been tested in real artworks. In this paper, we report on the application of this procedure for the first time on a contemporary oil easel painting with naturally aged varnish. The obtained results were compared with those achieved using traditional solvents, specifically a mixture of ligroin:acetone. Additionally, hot water was used to remove surface dirt. The performance of the different cleaning procedures was assessed with a range of techniques, including low-power microscopy, UV lamp illumination, laser-induced fluorescence (LIF), and laser-induced breakdown spectroscopy (LIBS). Of the tested treatments, the best performance is obtained by nanosecond laser irradiation at 213 nm using an adequate laser fluence (typically 0.14 J/cm2) that allows controlled and efficient removal of the outermost aged varnish layer without affecting the underlying non-aged varnish and paint layers.This research was funded by the Spanish State Research Agency (AEI) through the project SCOCHLAS (Study and Conservation of Cultural Heritage with Lasers, PID2019-04124RBI00/AEI/1013039/501100011033), by the Community of Madrid through the project Top Heritage- CM (Tecnologías en Ciencias del Patrimonio, S2018/NMT_4372), and by the H2020 project IPERION HS (Integrated Platform for the European Research Infrastructure ON Heritage Science, GA 871034). L. Maestro-Guijarro’s participation was financed by a Youth Guarantee contract (CAM20_IQFR_AI_06) from the Community of Madrid.There are 4 folders that correspond to each technic employed for the analysis of the cleaning procedures, and 1 for the cleaning conditions description. The folder titled "PHOTOS" contains: Fig. 1 Image of the picture. Selected cleaned areas; Fig. 2 UV light image of the artwork; Fig. 3 Digital microscopy of area 6 (before and after cleaning); Fig. 4 Fluorescence under UV lamp before and after cleaning. The folder titled “LIBS” contains: LIBS_withoutcleaning; LIBS_deionizedwater; LIBS_solventmixture; LIBS_213nm,0.10 Jcm2; LIBS_213nm,0.14 Jcm2. The folder for “LIF” contains: LIF_withoutcleaning; LIF_deionizedwater; LIF_solventmixture; LIF_213nm,0.10 Jcm2; LIF_213nm,0.14 Jcm2. The folder “FTIR” contains: FTIR_varnish. The folder "Cleaning conditions description" contains the file "Cleaning treatments".Peer reviewe

In-depth structural and compositional assessment of aged terpenoid varnish layers by nonlinear optical microscopy

11 pags., 6 figs., 3 tabs.Varnishes are employed in painted artworks for protection from atmospheric pollution and oxidation and for improving the esthetic appearance by providing an even and brilliant surface finish. Also, in some cases, colored varnishes are applied intentionally to modify the chromatic appearance of paintings. Varnishes undergo complex and differentiated structural and chemical changes over time depending on their composition and conservation conditions. The present work investigates the extent of degradation of the outermost layers of varnish coatings due to aging as a function of depth by using nonlinear optical microscopy (NLOM) in the modality of multiphoton excitation fluorescence (MPEF). This non-invasive technique has been employed for the determination of the thickness, with a microscopic axial and lateral resolution, of the affected regions of pictorial terpenoid varnish layers, such as dammar, mastic, shellac and sandarac, subjected to various types and degrees of aging, artificial, natural and a combination of both. A homemade nonlinear optical microscope, based on a tightly focused pulsed femtosecond laser emitting at 800 nm, was used for the investigation. Single-photon laser-induced fluorescence (LIF) measurements served to determine the degree of surface aging and the optimum NLOM-MPEF operating conditions and helped to interpret the results obtained by applying the latter. These results signpost the correlations between the extent of degradation, non-invasively determined by NLOM-MPEF, the type and length of aging, the nature of the varnish and the initial thickness of the varnish layer.This research has been funded by the Spanish State Research Agency (AEI) through project PID2019-104124RB-I00/AEI/1013039/501100011033, by the H2020 European project IPERION HS (Integrated Platform for the European Research Infrastructure ON Heritage Science, GA 871034), and by the Community of Madrid project Top Heritage-CM (Tecnologías en Ciencias del Patrimonio, S2018/NMT_4372). Support by CSIC Interdisciplinary Platform “Open Heritage: Research and Society” (PTI-PAIS) is acknowledged.Peer reviewe

Comparison of the Use of Traditional Solvents and Nanosecond 213 nm Nd:YAG Laser in Thinning Naturally Aged Varnish on a Contemporary Oil Easel Painting

The removal of aged varnish on artistic paintings is a delicate intervention and the use of UV laser for this purpose is of special relevance. In particular, the use of nanosecond-pulsed lasers operating at 213 nm has been noted to produce good results in mock-up samples, but it has not been tested in real artworks. In this paper, we report on the application of this procedure for the first time on a contemporary oil easel painting with naturally aged varnish. The obtained results were compared with those achieved using traditional solvents, specifically a mixture of ligroin:acetone. Additionally, hot water was used to remove surface dirt. The performance of the different cleaning procedures was assessed with a range of techniques, including low-power microscopy, UV lamp illumination, laser-induced fluorescence (LIF), and laser-induced breakdown spectroscopy (LIBS). Of the tested treatments, the best performance is obtained by nanosecond laser irradiation at 213 nm using an adequate laser fluence (typically 0.14 J/cm2) that allows controlled and efficient removal of the outermost aged varnish layer without affecting the underlying non-aged varnish and paint layers

LIBS vs XRF on underwater heritage: The silver coins of "Nuestra Señora de las Mercedes"

11 pags., 5 figs., 1 tab.This work presents a comparative investigation using two non-invasive elemental analytical techniques, X-ray fluorescence (XRF) and laser-induced breakdown spectroscopy (LIBS), for the chemical characterization of a real case study of underwater-corroded metals: the silver coins of the Spanish frigate “Nuestra Señora de las Mercedes”. A ship loaded with funds and products from the Viceroyalty of Peru, well known to had been sunk by the British Army in 1804 off the coast of Algarve and plundered more than two hundred years later by the commercial company Odyssey Marine Exploration. The combination of both techniques allows overcoming the complexity of the thick patinas covering the coins, compound by corrosion products and the deposits from the seabed. While XRF helps to answer inquiries associated with the conservation and restoration of the metallic pieces, LIBS can solve questions about their core composition and metallurgical techniques employed for their production.This research has been funded by the Spanish State Research Agency (AEI) through project PID2019-104124RB-I00/AEI/1013039/501100011033, by the H2020 European project IPER-ION HS (Integrated Platform for the European Research Infrastructure ON Heritage Science, GA 871034). Professional support of the CSIC Interdisciplinary Thematic Platform (PTI) Open Heritage: Research and Society (PTI-PAIS) is acknowledged