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A valuable step in the modeling of multiscale dynamical systems in fields such as computational chemistry, biology, and materials science is the representative sampling of the phase space over long time scales of interest; this task is not, however, without challenges. For example, the long term behavior of a system with many degrees of freedom often cannot be efficiently computationally explored by direct dynamical simulation; such systems can often become trapped in local free energy minima. In the study of physics-based multi-time-scale dynamical systems, techniques have been developed for enhancing sampling in order to accelerate exploration beyond free energy barriers. On the other hand, in the field of machine learning (ML), a generic goal of generative models is to sample from a target density, after training on empirical samples from this density. Score-based generative models (SGMs) have demonstrated state-of-the-art capabilities in generating plausible data from target training distributions. Conditional implementations of such generative models have been shown to exhibit significant parallels with long-established—and physics-based—solutions to enhanced sampling. These physics-based methods can then be enhanced through coupling with the ML generative models, complementing the strengths and mitigating the weaknesses of each technique. In this work, we show that SGMs can be used in such a coupling framework to improve sampling in multiscale dynamical systems. [ABSTRACT FROM AUTHOR]

Steady states are invaluable in the study of dynamical systems. High-dimensional dynamical systems, due to separation of time scales, often evolve toward a lower dimensional manifold M. We introduce an approach to locate saddle points (and other fixed points) that utilizes gradient extremals on such a priori unknown (Riemannian) manifolds, defined by adaptively sampled point clouds, with local coordinates discovered on-the-fly through manifold learning. The technique, which efficiently biases the dynamical system along a curve (as opposed to exhaustively exploring the state space), requires knowledge of a single minimum and the ability to sample around an arbitrary point. We demonstrate the effectiveness of the technique on the Müller–Brown potential mapped onto an unknown surface (namely, a sphere). Previous work employed a similar algorithmic framework to find saddle points using Newton trajectories and gentlest ascent dynamics; we, therefore, also offer a brief comparison with these methods. [ABSTRACT FROM AUTHOR]

Herein, we report on the preparation, structure, and magnetic characterization of FeCoCu nanowire arrays grown by DC electrodeposition inside self-assembled ordered nanopores of anodic aluminum oxide templates. A systematic study of their structure has been performed both in asprepared samples and after annealing in the temperature range up to 800 °C, although particular attention has been paid to annealing at 700 °C after which maximum magnetic hardening is achieved. The obtained nanowires have a diameter of 40 nm and their Fe0.28Co0.67Cu0.05 composition was confirmed by energy dispersive X-ray spectroscopy (EDS). Focused ion-beam lamellas of two samples (as-prepared and annealed at 700 °C) were prepared for their imaging in the high-resolution transmission electron microscopy (HRTEM) perpendicularly to the electron beam, where the obtained EDS compositional mappings show a homogeneous distribution of the elements. X-ray diffraction analysis, and selected area electron diffraction (SAED) patterns confirm that nanowires exhibit a bcc cubic structure (space group Im-3m). In addition, bright-dark field images show that the nanowires have a polycrystalline structure that remains essentially the same after annealing, but some modifications were observed: (i) an overall increase and sharpening of recrystallized grains, and (ii) an apparent shrinkage of the nanowires diameter. Obtained SAED patterns also show strong textured components with determined (111) and (112) crystalline directions parallel to the wires growth direction. The presence of both directions was also confirmed in the HRTEM images doing Fourier transform analyses. Magnetic measurements show strong magnetic anisotropy with magnetization easy axis parallel to the nanowires in as-prepared and annealed samples. The magnetic properties are tuned by suitable thermal treatments so that, maximum enhanced coercivity (∼2.7 kOe) and normalized remanence (∼0.91 Ms) values are achieved after annealing at temperature of 700 °C. The contribution of the changes in the crystalline structure, induced by the heat treatment, to the magnetic hardening of the FeCoCu nanowires is discussed. © 2014 AIP Publishing LLC. [ABSTRACT FROM AUTHOR]

We have synthesized two divanadates M2V2O7 (M2+ = Co2+ and Cu2+), that are known to show different and complex magnetic arrangements at low temperatures and have studied their dielectric behavior. We have observed a change in the slope of the dielectric constant at the magnetic transition temperature, result which confirms the existence of magnetodielectric coupling in these two divanadates. The origin of the magnetodielectric coupling seems to be different in the Cu- and Co-compounds, although in both cases it is related to their frustrated magnetic arrangement. In Cu2V2O7, the dielectric anomaly arises from a spin canting due to the antisymmetric exchange which is allowed by structural symmetry. In the Co-divanadate, the structural symmetry does not allow antisymmetric exchange but the compound shows correlation between the behavior of the dielectric constant and inverse magnetization, which points to a dependence of its electrical polarization with the pair correlation function of neighboring magnetic spins. [ABSTRACT FROM AUTHOR]

We present a detailed investigation on the magnetodielectric properties of Fe2OBO3, where we have found a magnetodielectric effect around 150% at room temperature and ν=2 kHz, that cannot solely arise from magnetoresistive extrinsic contributions. In addition, we find a crossover of the magnetodielectric response around TN, that we attribute to changes in the electronic microstructure of this compound that take place at that temperature. For TN the dielectric constant experiences a jump at a temperature dependent critical field that we relate to a partial melting of the charge ordering state. [ABSTRACT FROM AUTHOR]

We have investigated the propagation of terahertz (THz) surface plasmon polaritons (SPPs) on gratings formed by grooves structured in silicon wafers. These gratings exhibit a stop gap where SPPs are Bragg scattered. We observe a strong effect of the groove depth on the characteristics of the stop gap. To quantify the scattering strength of these structures we obtain the SPP attenuation length by measuring the transmission as a function of the number of grooves. We also determine the effective refractive index of the Bragg gratings using two different approaches: by measuring the transmittance through the gratings at different angles of incidence and from the phase of the transmitted THz pulses. The two approaches give results in good agreement. [ABSTRACT FROM AUTHOR]

The magnetic anisotropy induced in amorphous magnetic ribbons by applying a magnetic field to the melt during the solidification process is analyzed. Using a model based on the magnetization curve and on the evolution of the uniaxial torque with the applied magnetic field, the volume fractions of the sample affected by the different magnetic anisotropies are obtained for the ribbons of composition Fe80B20 and Co70Mn5Fe1Mo1Si14B9. The results are compared with those obtained in the ribbons of the same composition but with anisotropies induced by the static magnetic annealing. From these results, the different sources of the field-quenching-induced magnetic anisotropy in those amorphous magnetic ribbons are analyzed. [ABSTRACT FROM AUTHOR]

We study the nonlinear current-voltage (I - V) characteristics and analyze the voltage-dependent tunneling conductance in nanoparticles of La[SUB2/3]A[SUB1/3]MnO[SUB3] (A=Ca, Sr). The powders were prepared by different wet-chemical routes and low calcination temperatures were used to obtain an average particle size D≈30 nm. The data are comprehensively explained in terms of the tunneling picture, which allows one to estimate the height of the grain boundary insulating barrier (ϕ) for each sample. For constant D, our results show that the sample preparation route is mainly responsible for the value of ϕ in nanoparticles, while the Coulomb gap in the Coulomb blockade regime is ∼3 times higher for Sr- than for Ca-doping. We also show that a small fraction of the barriers contribute to the nonlinear transport, and the current is mainly carried through low-resistive percolated paths. In addition, despite the different barrier strengths, the low-field magnetoresistance (LFMR) is similar for all samples, implying that ϕ is not the fundamental parameter determining the LFMR. [ABSTRACT FROM AUTHOR]

We report the effect of progressive reduction of the annealing temperature on the magnetocaloric effect (MCE) of La[sub 2/3]Ca[sub 1/3]MnO[sub 3-δ] nanoparticles synthesized by the sol-gel technique. With this method, we are able to obtain particle diameters ranging form 60 to 500 nm. The peak in the MCE at the ferromagnetic to paramagnetic phase transition is strongly reduced as annealing temperature does, due to loss of the intrinsic first-order magnetic phase transition. This opens up a new way in which to tune the intrinsic properties of mixed-valence manganites, most of which are associated with the first-order character of the magnetic transition. [ABSTRACT FROM AUTHOR]

Throughout a complete electron spin resonance (ESR) and magnetization study of La[sub 0.5]Ca[sub 0.5]MnO[sub 3], we discuss about the nature of the complex phase-segregated state established in this compound below T∼ 210 K. Between T[sub N]... T... T[sub c], the ESR spectra shows two lines characteristic of two different magnetic phases. From the resonance field (H[sub r]) derived for each line, we argue that the incommensurate-charge-ordering phase (ICO) which coexists with ferromagnetic-metallic (FMM) clusters in this temperature interval, is mainly paramagnetic and not antiferromagnetic. The FMM/ ICO ratio can be tuned with a relatively small field, which suggests that the internal energy associated with those phases is very similar. Below T[sub N], there is an appreciable ferromagnetic (FM) contribution to the magnetization and the ESR spectra indicates the presence of FM clusters in an antiferromagnetic matrix (canted). Our results show that ESR could be a very useful tool to investigate the nature of the phase-separated state now believed to play a fundamental role in the physics of mixed valent manganites. [ABSTRACT FROM AUTHOR]

The dependence of the ac-magnetic susceptibility of La[sub 0.85]Sr[sub 0.15]CoO[sub 3] on the annealing temperature used during synthesis is addressed. Such dependence has been previously attributed to compositional inhomogeneities. Nevertheless, the presence of distinct phases with different chemical compositions is excluded after explorations by several techniques. Instead it is proposed that an electronic phase separation takes place in the material, whose state is changed after charge-carrier redistributions due to the thermal history of the samples, analogously to parent manganese-based perovskites. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

This work focuses on the structural and magnetic characterization of arrays of cobalt nanowires, with diameters in the range 100-400 nm and lengths of L≤6 μm, produced by electrodeposition in polycarbonate membrane pores. Diffraction patterns of Co nanowires indicate that Co is stabilized in the hcp structure with a preferential (0001) texture oriented close to the perpendicular direction of the wires axes. Magnetic measurements at room temperature reveal that magnetization undergoes a change in the easy axis as the length of the wires increases. Clearly, the easy axis of the shortest wires is oriented along the axis of the wire. In the case of the longest wires, a crossover of the easy axis is observed, from the perpendicular to the parallel direction to the wire for the shortest. This magnetic behavior is explained through a simple magnetostatic model, which takes into account the dipolar interactions among wires, the demagnetizing field, and the magnetocrystalline anisotropy of Co. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Magnetotransport properties of manganite/insulator composites are studied in this article. By merging the half metallic character of La[sub 2/3]Ca[sub l/3]MnO[sub 3] and the mixed composition with alumina grains dispersed in the structure we have been able to increase three times intergranular magnetoresistance around the percolation threshold. The transport properties have been studied employing a theoretical model for ferromagnetic-insulator systems and a two channel equation in order to reproduce the behavior of resistivity in the whole temperature range. The percolation theory is introduced to try to understand and improve the fascinating properties of these mixed systems. [ABSTRACT FROM AUTHOR]

Presents information on a study which showed how colossal magnetoresistance effect (CMR) could be tuned in polycrystalline mixed valence manganite La...Ca...MnO... by changing grain size. Experimental procedures; Results and discussion; Conclusions.

Presents a study that investigated the thermal treatment dependence of the dynamic magnetic behavior of copper oxides. Effect of thermal treatment on the magnetic properties of copper oxides; Experimental details; Result and discussions.

Magnetite nanoparticles about 10 nm sized were synthesized by the polyol method. Zero-field-cooled (ZFC)-FC measurements showed a blocking temperature ~170K and the absence of the Verwey transition. They were subsequently consolidated by spark plasma sintering at 750 °C for 15 min, leading to a high density (92% of the theoretical density), solid body, with grains in the 150 nm range. X-ray diffraction patterns exhibited a spinel single phase with cell parameters corresponding to the magnetite structure. Magnetic measurements showed a decrease of coercivity from 685 Oe (54.5 kA/m) at 118K to 90 Oe (7.2 kA/m) at 139 K. ZFC measurements at 25 Oe presented a three-fold magnetization increase as temperature increased; a small transition between 116 and 117.5 K, followed by a larger one from 117.6 to 124 K. The first transition can be associated with a complex crystallographic transition and delocalization of Fe2+-Fe3+, while the second one can be attributed to spin reorientation due to the magnetocrystalline anisotropy constant (K1) change of sign as previously observed only in magnetite single crystals. [ABSTRACT FROM AUTHOR]

From data of initial magnetization isotherms, the magnetic entropy change ΔS[sub M] of the series of ferromagnetic perovskites La[sub 2/3](Ca[sub 1-χ]Sr[sub χ])[sub l/3]MnO[sub 3], with χ=0, 0.05, 0.15, 0.25, 0.50, 0.75 and 1, has been measured near their Curie temperatures. The results go from 3.7 Jkg[sup -l]K[sup -1] for La[sub 2/3]Ca[sub l/3]MnO[sub 3] to 1.5 J kg[sup -1] K[sup -1] for La[sub 2/3]Sr[sub l/3]MnO[sub 3]. Nevertheless, the evolution of ΔS[sub M] with χ is not monotonic, it shows a steep decrease between χ = 0.05 and χ = 0.15. This point corresponds to a tolerance factor t=0.92, at which the system changes from orthorhombic (Pbnm) to rhombohedral (R&3macr;c) structure, and the magnetic phase transition from first to second order. Provided that rhombohedral symmetry forbids static long-range cooperative Jahn-Teller distortions, present in orthorhombic samples, we interpret our results as the strong increase of lattice effects in them. The anomalous thermal expansion at the Curie temperature, due to these lattice effects, is thought to underlie the jump in ΔS[sub M] with χ. [ABSTRACT FROM AUTHOR]

A complete characterization of the magnetotransport and magnetoelastic properties of two classical examples of half doped manganites, Nd[sub 0.5]Sr[sub 0.5]MnO[sub 3] (NSMO) and La[sub 0.5]Ca[sub 0.5]MnO[sub 3] (LCMO), was carried out by electrical resistivity, magnetoresistance, thermoelectric power, electron spin resonance (ESR), and thermal expansion measurements. We have identified a mixed paramagnetic (charge localized) plus ferromagnetic (FM) (conductive) state between the low temperature antiferromagnetic (AF) and high temperature paramagnetic (itinerant) phases, which in the case of LCMO exists over a temperature range of about 100 K. The magnetic field completely separates the FM and AF phases, suppressing the intermediate paramagnetic-localized phase. This mixed state is only observed in a narrow temperature interval for NSMO, and shows how the relative strength of the competing phases can be tuned by the lattice distortion. We also observed a large gap at the charge ordering temperature in the activation energy of the resistivity, which is almost independent of the sample. ESR results will be presented to show that this technique could be a very useful tool with which to investigate the multiphase microscopic state characteristic of manganites. [ABSTRACT FROM AUTHOR]

Spin dynamics of the Mn-site substituted colossal magnetoresistance system were studied by means of electron paramagnetic resonance (EPR) and dc magnetic susceptibility in La[sub 2/3]Ca[sub 1/3]Mn[sub 1-x]Co[sub x]O[sub 3] (0≤x≤0.1,Δx=0.025). A dramatic increase in the high temperature limiting value for the EPR linewidth (ΔH[sub pp](∞)) was observed with doping. Structural analysis revealed that only negligible changes are produced in bond distances and angles at these low doping levels. On the other hand, dipolar contribution to ΔH[sub pp](∞) was estimated in a few Gauss. To explain the effect of doping on ΔH[sub pp](∞), we propose here a scenario including fast Mn-spin lattice relaxation through paramagnetic Co ions. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The weak ferromagnetic transition of T[sup ′]-phase Gd[sub 2]CuO[sub 4] single crystals has been studied by dc-magnetization measurements. Weak ferromagnetism is generated in this material by a very slight canting of the Cu moments from a perfect antiferromagnetic structure. This canting enables the inspection of the magnetic state of the Cu sublattice by pure magnetic methods. The critical exponents of the transition are calculated, γ=1.32(2), β=0.34(1). Nevertheless, a rapid evolution of β to a 2D XY behavior is observed below the critical temperature. It is interpreted as evidence of a transition in the 2D system, namely CuO[sub 2] planes, that behave as 3D at the critical point due to the effect of the interlayer interaction along the c-axis. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The magnetic and electrical properties of R[sub 1-x]Sr[sub x]CoO[sub 3] materials (R=La, Pr, Nd, Gd) (0≤x≤0.50) are studied. Rare-earths with angular momentum L≠0 enhance coercive field values. They are maximum for R=Nd (the highest L) and much smaller for Gd and La (L=0). The result is interpreted as the contribution of the L–S coupling in the rare-earth to the magnetic anisotropy of the system. Electrical conductivity is improved with Sr doping, but increases of rare-earth atomic number lead to decreases of conductivity. This is attributed to the increase of lattice distortions, due to the smaller R[sup 3+] ionic size, and to the effect of the rare-earth on the spin state of cobalt ions. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Reports on a dynamical magnetic susceptibility study on La1-xSrxCoO3 perovskite samples obtained by a coprecipitation method. Preparation of the samples; Dc magnetic measurements.

Presents information on a study that measured the microwave absorption associated with a magnetic resonance of the weak-ferromagnetic component of the magnetization. Experimental procedure; Results and discussion.

Discusses a study on the structural and magnetic characterization of cobalt particles with sodium. Properties of single domain magnetic particles; Experimental setup; Results and discussion.

Presents a study that examined the current-voltage curves in yttrium-barium-copper-oxygen (YBaCuO) rings of fixed size but of different oxygen content. Information on the current voltage curves of liquid-nitrogen temperature of YBaCuO rings; Discussion on current-voltage curves.

Discusses the relationship between coercivity, magnetic viscosity, and particle size in barium hexaferrite samples covering several orders of magnitude in particle dimensions. Preparation of samples and experimental techniques used; Temperature dependence of the critical field of all the samples; Types of reversal mechanisms consistent with dependence.

Presents magnetic susceptibility studies in Gd[sub2]CuO[sub4] below 300 K. Background on rare earth cuprates; Experimental techniques; Results.

Provides information on a study that investigated high-temperature magnetic relaxation in polycrystalline magnetite. Experimental procedure; Results and discussion on the study.

Presents a study that described the synthesis of Gd[sub2-x]Ce[subx]CuO[sub4] (with X=0.00, 0.05, 0.10 and 0.15) using a sol-gel technique and water-in-oil microemulsions. Description of techniques to obtain particles of different sizes; Magnetization and ac susceptibility measurements; Discussion on the differences between the zero-field-cooling and the field-cooling magnetization curves.

Focuses on a study which observed weak ferromagnetism in gadolinium[sub 2] copper oxide[sub 4] which was induced by the external field above the Néel temperature T[sub N] alternating current measurements. Comparison of the shift of the electron-spin-resonance line of the Gadolinium ions as a function of temperature T, deltaH[sub r](T) with the static internal field H[sub t](T); Methodology of the study; Results and discussion.

Presents information on a study which examined the ferromagnetism and spin-glass-like behavior of a polycrystalline with tetragonal structure. Description of a tetragonal crystal structure; Methodology of the study; Results and discussion.

We determine the angle and polarization dependent emission from 1.75 mm and 2.50 mm long InP nanowires by using cathodoluminescence polarimetry. We excite the vertical wires using a 5 keV electron beam, and find that the 880 nm bandgap emission shows azimuthally polarized rings, with the number of rings depending on the wire height. The data agree well with a model in which spontaneous emission from the wire emitted into the far field interferes with emission reflected off the substrate. From the model, the depth range from which the emission is generated is found to be up to 400 nm below the top surface of the wires, well beyond the extent of the primary electron cloud. This enables a probe of the carrier diffusion length in the InP nanowires. [ABSTRACT FROM AUTHOR]

We demonstrate that an array of optical antennas may render a thin layer of randomly oriented semiconductor nanocrystals into an enhanced and highly directional source of polarized light. The array sustains collective plasmonic lattice resonances, which are in spectral overlap with the emission of the nanocrystals over narrow angular regions. Consequently, different photon energies of visible light are enhanced and beamed into definite directions. [ABSTRACT FROM AUTHOR]

The energy barrier distribution Eb of five samples with different concentrations x of Ni nanoparticles using scaling plots from ac magnetic susceptibility data has been determined. The scaling of the imaginary part of the susceptibility χ″(ν,T) versus T ln(t/τ0) remains valid for all samples, which display Ni nanoparticles with similar shape and size. The mean value b> increases appreciably with increasing x, or more appropriately with increasing dipolar interactions between Ni nanoparticles. We argue that such an increase in b> constitutes a powerful tool for quality control in magnetic recording media technology where the dipolar interaction plays an important role. [ABSTRACT FROM AUTHOR]

We report the optimization of the dielectric properties of La2/3Ca1/3MnO3. This is achieved by synthesizing this material with small particle size, strategy that reduces the conductivity of the sample and its dielectric losses, while retaining a reasonably high dielectric permittivity and a good magnetocapacitive response. In order to further improve the properties of these nanoparticles, we have also prepared core-shell composites La2/3Ca1/3MnO3@SiO2 but in this case the magnetocapacitive effect is strongly reduced. [ABSTRACT FROM AUTHOR]

This work describes an integrated device comprising microfluidic channels and incorporated spin-valve sensors sensitive enough to count, determine the magnetic orientation, flowing height, and speed of single micron-sized magnetic beads moving with velocities of 8–35 mm/s. Sensor signals of 3–100 μVp-p correspond to bead moments at different directions indicating a physical rotation of the beads and a slow response (seconds) of the bead moment to magnetizing field changes. [ABSTRACT FROM AUTHOR]

We report the thermoelectric figure of merit of chromium nitride, CrN, and its optimization through hole-doping. CrN is a degenerate semiconductor with large thermoelectric power, reaching -185 μV/K at 420 K. The resistivity can be reduced through hole-doping in the series Cr1-xVxN, keeping a large thermopower. The thermal conductivity of CrN is rather low compared to other transition-metal nitrides, reaching its minimum value of 1.0 W/m K at 267 K. The largest ZT=0.04 was measured for Cr0.9V0.1N at room temperature. Our results suggest that CrN could be a good starting point for the design of a thermoelectric material with optimal mechanical properties. [ABSTRACT FROM AUTHOR]

Giant birefringence is demonstrated in ensembles of randomly grown, vertically aligned semiconductor nanowires. Bottom-up fabrication of epitaxial semiconductor nanowires grown using the vapor-liquid-solid mechanism yields a highly anisotropic photonic metamaterial. The birefringence in the material is shown to depend on the nanowire length. Short nanowires with a volume filling fraction around 50% exhibit the strongest birefringence, in agreement with effective medium theories. A large difference is found between the in-plane and out-of-plane refractive indices of Δn=0.8, exceeding by a factor of 75 the natural birefringence of quartz and by more than a factor of 2 that of inverted artificial materials. [ABSTRACT FROM AUTHOR]

We report a rather high dependence of the dielectric permittivity on the magnetic field in La2/3Ca1/3MnO3. The variation is maximum at around 270 K, little above the Curie temperature TC, and it reaches a 35% under only 0.5 T. We attribute this phenomenon to the space-charge or interfacial polarization produced between the insulator and the metallic regions segregated intrinsically in the material above TC. [ABSTRACT FROM AUTHOR]

We report a rather high dependence of the dielectric permittivity on the magnetic field in La2/3Ca1/3MnO3. The variation is maximum at around 270 K, little above the Curie temperature TC, and it reaches a 35% under only 0.5 T. We attribute this phenomenon to the space-charge or interfacial polarization produced between the insulator and the metallic regions segregated intrinsically in the material above TC. [ABSTRACT FROM AUTHOR]

A major challenge in the development of surface plasmon optics or plasmonics is the active control of the propagation of surface plasmon polaritons (SPPs). Here, we demonstrate the feasibility of low-frequency active plasmonics using semiconductors. We show experimentally that the Bragg scattering of terahertz SPPs on a semiconductor grating can be modified by thermal excitation of free carriers. The transmission of SPPs through the grating at certain frequencies can be switched completely by changing the temperature less than 100 °C. This semiconductor switch provides a basis for the development of low-frequency surface-plasmon optical devices. [ABSTRACT FROM AUTHOR]

Magnetic properties of the Sr-doped BaCoO3 are explained on the basis of ab initio calculations and the analysis of experimental literature. Formation of magnetic clusters bigger than in the parent compound and an increase in the blocking temperature are observed. Superparamagnetism remains at room temperature. The possibility of tuning the size and properties of the magnetic clusters with doping is explored. [ABSTRACT FROM AUTHOR]

Magnetic properties of the Sr-doped BaCoO3 are explained on the basis of ab initio calculations and the analysis of experimental literature. Formation of magnetic clusters bigger than in the parent compound and an increase in the blocking temperature are observed. Superparamagnetism remains at room temperature. The possibility of tuning the size and properties of the magnetic clusters with doping is explored. [ABSTRACT FROM AUTHOR]

We report the dielectric response of La1.5Sr0.5NiO4, a system that experiences charge ordering above room temperature (TCO=480 K) and a rearrangement of its charge-order pattern in the temperature region 160–200 K. A careful analysis of the role of the electrical contacts used, sample thickness, and grain size on the experimental data allows us to determine that this material exhibits a high intrinsic dielectric constant. In addition, the temperature dependence of the dielectric constant, that shows a maximum in the region of the rearrangement of the charge-order pattern, points to a link between the two phenomena. [ABSTRACT FROM AUTHOR]