Attribution of paintings is a critical problem in art history. This study extends machine learning analysis to surface topography of painted works. A controlled study of positive attribution was designed with paintings produced by a class of art students. The paintings were scanned using a confocal optical profilometer to produce surface data. The surface data were divided into virtual patches and used to train an ensemble of convolutional neural networks (CNNs) for attribution. Over a range of patch sizes from 0.5 to 60 mm, the resulting attribution was found to be 60 to 96% accurate, and, when comparing regions of different color, was nearly twice as accurate as CNNs using color images of the paintings. Remarkably, short length scales, as small as twice a bristle diameter, were the key to reliably distinguishing among artists. These results show promise for real-world attribution, particularly in the case of workshop practice.

Freestanding magnetic Ni nanoparticles are obtained by γ-radiation induced synthesis out of aqueous precursor solutions.

Functional oxide nanocomposites, where the individual components belong to the family of strongly correlated electron oxides, are an important class of materials, with potential applications in several areas such as spintronics and energy devices. For these materials to be technologically relevant, it is essential to design low-cost and scalable synthesis techniques. In this work, we report a low-temperature and scalable synthesis of prototypical bi-magnetic LaFeO3-CoFe2O4 nanocomposites using a unique sol-based synthesis route, where both the phases of the nanocomposite are formed during the same time. In this bottom-up approach, the heat of formation of one phase (CoFe2O4) allows the crystallization of the second phase (LaFeO3), and completely eliminates the need for conventional high-temperature annealing. A symbiotic effect is observed, as the second phase reduces grain growth of the first phase, thus yielding samples with lower particle sizes. Through thermogravimetric, structural, and morphological studies, we have confirmed the reaction mechanism. The magnetic properties of the bi-magnetic nanocomposites are studied, and reveal a distinct effect of the synthesis conditions on the coercivity of the particles. Our work presents a basic concept of significantly reducing the synthesis temperature of bi-phasic nanocomposites (and thus also the synthesis cost) by using one phase as nucleation sites for the second one, as well as using the heat of formation of one phase to crystallize the other.

In the present work, we report the preparation of multiferroic PbZr0.52Ti0.48O3 (PZT)/CoFe2O4 (CFO) nanocomposites using a new synthesis technique that can maximize the surface area of contact, and hence, the interfacial coupling between the ferroelectric (PZT) and ferrimagnetic (CFO) phases. The samples have been characterized using X-ray diffraction (XRD) and transmission electron microscopy (TEM), and the physical (magnetic and dielectric) properties have been investigated. XRD confirms the presence of the desired PZT and CFO phases in the samples without any undesired secondary phases. We also observe a reduction in the particle size of CFO in the nanocomposites as evidenced by a line broadening of the XRD reflections corresponding to the pure CFO phase. The nanocomposites show hysteresis loops and ferrimagnetic-like behaviors in their M vs H curves at room temperature, even for samples with very low fraction of the CFO phase. The coercivity of the nanocomposites is marginally larger compared to that of pure CFO, which can be due to the change in magnetic anisotropy of the CFO phase due to its reduced particle size in the nanocomposites. Room temperature polarization versus electric field measurements show a significant increase in the coercive field after the incorporation of CFO inside the PZT matrix. This work illustrates a simple, cost-effective synthesis technique that can be used to prepare nanocomposites of functional materials with desired room temperature functionalities and enhanced interfacial coupling between the two phases.

Bi-phasic composite films are generally grown as multilayers that result in layer-by-layer morphology with each layer having a distinct chemical composition. In this work, we report an all-in-one chemical synthesis technique combined with spin-coating to prepare single-layer bi-magnetic LaFeO3 (LFO)-CoFe2O4 (CFO) composite thin films with both phases co-existing in the same layer. The films have been characterized using X-ray diffraction (XRD) and transmission electron microscopy (TEM), and the magnetic properties have been probed using dc magnetometry at room and low temperature. The unique synthesis technique followed ensures homogeneity of the two phases on the nanoscale with grain sizes similar to 10 nm for CFO and few tens of nm for LFO, as observed from TEM images. XRD confirms the presence of only the desired LFO and CFO phases in the films without any undesired secondary phases. Magnetic hysteresis loops reveal a coercivity of similar to 0.2 T at room temperature that increases by nearly one order of magnitude at T = 5 K. The all-in-one synthesis technique reported here can be used to prepare different bi-phasic composites in the form of single-layer two-dimensional films as well as zero-dimensional nanoparticles by a suitable modification of the precursors, solvents, and chelating agents.

Magnetic nanocomposites constitute a vital class of technologically relevant materials, in particular for next-generation applications ranging from biomedicine, catalysis, and energy devices. Key to designing such materials is determining and controlling the extent of magnetic coupling in them. In this work, we show how the magnetic coupling in bi-magnetic nanocomposites can be controlled by the growth technique. Using four different synthesis strategies to prepare prototypical LaFeO3-CoFe2O4 and LaFeO3-Co0.5Zn0.5Fe2O4 nanocomposite systems, and by performing comprehensive magnetic measurements, we demonstrate that the final material exhibits striking differences in their magnetic coupling that is distinct to the growth method. Through structural and morphological studies, we confirm the link between the magnetic coupling and growth methods due to distinct levels of particle agglomeration at the very microscopic scale. Our studies reveal an inverse relationship between the strength of magnetic coupling and the degree of particle agglomeration in the nanocomposites. Our work presents a basic concept of controlling the particle agglomeration to tune magnetic coupling, relevant for designing advanced bi-magnetic nanocomposites for novel applications.

A detailed study of the structural and magnetic properties of polycrystalline hollow gamma-Fe2O3 nanoparticles of similar to 9.4 nm size was performed. High-resolution transmission electron microscopy images confirmed the crystalline structure and the presence of a ultrathin shell thickness of similar to 1.4 nm, implying a very high surface/volume ratio. These hollow nanoparticles were investigated using zero-field and in-field Fe-57 Mossbauer spectrometry. The zero-field hyperfine structure suggests some topological disorder, whereas the infield one shows the presence of a comp magnetic structure that can be fairly described as two opposite pseudosperomagnetic sublattices attributed to octahedral and tetrahedral iron sites. Such an unusual feature is consistent with the presence of noncollinear spin structure originated from the increased surface due to the hollow morphology. Such a complex local spin structure evidenced from Mossbauer experiments was correlated with exchange bias coupling showing at low temperature by magnetization measurements. Monte Carlo simulations on a ferrimagnetic hollow nanoparticle unambiguously corroborate the critical role of the surface anisotropy on the noncollinearity of spin structure in our samples.

Magnetic properties of iron oxide nanoparticles with spinel structure are strictly related to a complex interplay between cationic distribution and the presence of a non-collinear spin structure (spin canting). With the aim to gain better insight into the effect of the magnetic structure on magnetic properties, in this paper we investigated a family of small crystalline ferrite nanoparticles of the formula CoxNi1-xFe2O4 (0 ≤x≤ 1) having equal size (≈4.5 nm) and spherical-like shape. The field dependence of magnetization at low temperatures indicated a clear increase of magnetocrystalline anisotropy and saturation magnetization (higher than the bulk value for CoFe2O4: ∼130 A m(2) kg(-1)) with the increase of cobalt content. The magnetic structure of nanoparticles has been investigated by Mössbauer spectroscopy under an intense magnetic field (8 T) at a low temperature (10 K). The magnetic properties have been explained in terms of an evolution of the magnetic structure with the increase of cobalt content. In addition a direct correlation between cationic distribution and spin canting has been proposed, explaining the presence of a noncollinear spin structure in terms of superexchange interaction energy produced by the average cationic distribution and vacancies in the spinel structure.