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Even a single-component liquid may have more than two kinds of isotropic liquid states. The transition between these different states is called a liquid–liquid transition (LLT). An LLT has been considered to be a rather rare phenomenon, in particular for molecular liquids. Very recently, however, we found an LLT in triphenyl phosphite, which may be the first experimental observation of an LLT for molecular liquids. Here we report convincing evidence of the second example of LLT for another molecular liquid, n-butanol. Despite large differences in the chemical structure and the molecular shape between triphenyl phosphite and n-butanol, the basic features of the transformation kinetics are strikingly similar. This suggests that an LLT may not be a rare phenomenon restricted to specific liquids, but may exist in various molecular liquids, which have a tendency to form long-lived locally favoured structures due to anisotropic interactions (e.g., hydrogen bonding).

There has been considerable recent interest in the design of diluted magnetic semiconductors, with a particular focus on the exploration of different semiconductor hosts. Among these, the oxide-based diluted magnetic semiconductors are attracting increasing attention, following reports of room temperature ferromagnetism in anatase TiO₂ and wurtzite ZnO doped with a range of transition metal ions. In this review we summarize the current status of oxide-based diluted magnetic semiconductors, and discuss the influence of growth method, substrate choice, and temperature on the microstructure and subsequent magnetic properties of thin films. We outline the experimental conditions that promote large magnetization and high ferromagnetic Curie temperature. Finally, we review the proposed mechanisms for the experimentally observed ferromagnetism and compare the predictions to the range of available data.

We review recent progress in the field of multiscale hybrid computer simulations of materials, and present an overview of a novel scheme that links arbitrary atomistic simulation techniques together in a truly seamless manner. Rather than constructing a new hybrid Hamiltonian that combines different models, we use a unique short range classical potential and continuously tune its parameters to reproduce the atomic trajectories at the prescribed level of accuracy throughout the system.

We report Raman scattering measurements on the spin ladder compound (C₅H₁₂N)₂CuBr₄. Pronounced multiphonon scattering is observed up to eighth-order, arising from the Franck–Condon process. Furthermore, a two-magnon continuum is seen with frequencies around 18 cm⁻¹ at low temperatures. Its symmetric line shape suggests a substantial hopping of triplets along the leg of the ladder. Thus, the studied system is considered to represent a two-leg ladder with coupling constants in the intermediate regime between the strong and the isotropic limit.

A theoretical investigation is made of acoustic wave propagation in one-dimensional phononic bandgap structures made of slender tube loops pasted together with slender tubes of finite length according to a Fibonacci sequence. The band structure and transmission spectrum is studied for two particular cases. (i) Symmetric loop structures, which are shown to be equivalent to diameter-modulated slender tubes. In this case, it is found that besides the existence of extended and forbidden modes, some narrow frequency bands appear in the transmission spectra inside the gaps as defect modes. The spatial localization of the modes lying in the middle of the bands and at their edges is examined by means of the local density of states. The dependence of the bandgap structure on the slender tube diameters is presented. An analysis of the transmission phase time enables us to derive the group velocity as well as the density of states in these structures. In particular, the stop bands (localized modes) may give rise to unusual (strong normal) dispersion in the gaps, yielding fast (slow) group velocities above (below) the speed of sound. (ii) Asymmetric tube loop structures, where the loops play the role of resonators that may introduce transmission zeros and hence new gaps unnoticed in the case of simple diameter-modulated slender tubes. The Fibonacci scaling property has been checked for both cases (i) and (ii), and it holds for a periodicity of three or six depending on the nature of the substrates surrounding the structure.

We have simulated using molecular dynamics the thermal stability and crystallization kinetics of nanometre-sized clusters of amorphous Si embedded in crystalline Si, which are of interest for phase-change memory devices. We have calculated the interfacial and bulk excess energies of the amorphous clusters, and studied their crystallization kinetics at 700–1500 K. At temperatures below (above) 1150 K the activation energy is 0.73 ± 0.04 eV (1.52 ± 0.07 eV), indicating a change of mechanism at 1150 K. We predict the stability of much larger amorphous clusters by extrapolating our simulation data using an analytic model.

Synchrotron x-ray powder diffraction was used to study Sc₂Mo₃O₁₂ and Al₂W₃O₁₂ at high pressure in a DAC. Both compounds adopt the orthorhombic Sc₂W₃O₁₂ structure under ambient conditions and exhibit anisotropic negative thermal expansion. A phase transition from orthorhombic (Pnca) to monoclinic (P 2₁/a) symmetry was observed at ∼0.25 GPa for Sc₂Mo₃O₁₂ and at ∼0.1 GPa for Al₂W₃O₁₂ associated with a volume reduction of ∼1.5–2%. A second crystalline to crystalline phase transition was clearly seen only for Sc₂Mo₃O₁₂ (2.5–3.0 GPa). Peak broadening and almost complete amorphization were observed for Sc₂Mo₃O₁₂ at ∼8 GPa, and this was not fully reversible on decompression. At 7 GPa, the amorphization of Al₂W₃O₁₂ was not as advanced as for the molybdate and on decompression crystalline material was recovered. The compressibility of orthorhombic Sc₂Mo₃O₁₂ is highly anisotropic, but it is almost isotropic for both monoclinic Sc₂Mo₃O₁₂ and Al₂W₃O₁₂. Both compounds show a reduction in their bulk moduli (K₀) at the orthorhombic to monoclinic transition: 32(2) GPa for orthorhombic and 16(1) GPa for monoclinic Sc₂Mo₃O₁₂, and 48 GPa for orthorhombic and 28(1) GPa for monoclinic Al₂W₃O₁₂. Sc₂Mo₃O₁₂ displays very similar high pressure behaviour to the previously studied Sc₂W₃O₁₂.

A study of the microstructures and magnetic properties of nanosize Zn ferrite (ZnFe₂O₄), Mn ferrite (MnFe₂O₄), and the cation deficit Zn–Mn ferrites Zn_0.70Mn_0.23Fe_1.89O₄ (S1), Zn_0.41Mn_0.50Fe_1.84O₄ (S2) and Zn_0.18Mn_0.67Fe_1.85O₄ (S3) was performed. The crystallite size for all samples was determined by x-ray powder diffraction (XRPD) analysis using four different methods, and was close to the particle size found from transmission electron microphotography. Among different methods of XRPD line broadening analysis it seems that the cubic harmonic function method is more precise and reliable than the Warren–Averbach and simplified integral breadth methods. M(T) and M(H) magnetization curves at different fields/temperatures indicate superparamagnetic behaviour of the samples. Asymmetric hysteresis loops and differences in coercive fields, H_C−(FC) − H_C−(ZFC), are discussed by both the core/shell model of nanoparticles and spin canting. The magnetic measurements with a maximum in the FC magnetization branches, the difference in M/M_S versus H/T curves above T_max (temperature of maximum in ZFC magnetization), the nonlinearity in H_C versus T^1/2, the remanence/saturation ratio value, M_R/M_S and observation of the Almeida–Thouless line for low-field magnetization data (T_max versus H^2/3) indicate that the samples consist of an interacting ferrite nanoparticle ensemble.

The preferred site of Mg segregation at Σ = 11(113) grain boundaries in Al and the effects of Mg segregation on grain boundary cohesion have been investigated through first-principle pseudopotential total energy calculations. The results show that the Mg atom prefers to occupy the 'looser' site at the grain boundary of Al but not the 'tighter' site. Furthermore, on basis of the thermodynamic theory of Rice and Wang, we have studied the effect of Mg segregation on the grain boundary cohesion of Al. Our total energy calculations show that Mg behaves as an embrittler. Additionally, the cohesive energies for a pure Al boundary and an Al boundary with Mg segregation have been calculated in this paper. The calculated results indicate that the cohesion of an Al grain boundary with Mg segregation is weaker than that of a pure Al grain boundary. The total charge density of the gain boundary also demonstrates that the Mg atom forms weaker metallic bonds with neighbouring Al atoms in the grain boundary region.

We have investigated the partial densities of states of Sr₂FeMoO₆ by applying soft x-ray emission spectroscopy (XES) to the Fe L, the Mo M and the O K edges. We discuss the results in the light of complementary measurements of the valence band by means of x-ray photoelectron spectroscopy (XPS) and first-principles generalized gradient approximation (GGA) and LDA +U band structure calculations.

A series of Fe-substituted manganites Bi_0.5Ca_0.5Fe_xMn_1−xO₃ (0≤x≤0.6) was synthesized by ceramic technology. The crystal lattice parameters change monotonically with increasing Fe substitution for Mn as found from x-ray powder diffraction and neutron diffraction investigations at room temperature. Magnetic properties were studied between 5 and 1300 K in fields up to 16 kOe. All the compounds are antiferromagnetic below a certain temperature, which decreases with increasing Fe substitution, and for x≥0.1 the antiferromagnetism is accompanied by a weak ferromagnetism. The charge/orbital order exists in the pure form for the compounds without or with very low Fe substitution (x = 0 and 0.05). A new magnetic cluster state exists in the paramagnetic region of manganites with Fe substitution x≥0.3, but only in the presence of magnetic field.

The conductivity of compounds measured between 100 and 600 K is of semiconducting type, and there is no magnetoresistivity effect in fields up to 7 kOe.

There have been recent reports of charge ordering around x = 0.5 in the bilayer manganites like La_2−2xSr_1+2xMn₂O₇. At x = 0.5, there appears to be a coexistence region of layered A-type antiferromagnetic order and charge order. There are also reports of orbital order in this region without any Jahn–Teller effect. Based on physical grounds, this region is investigated from a model that incorporates the two e_g orbitals at each Mn site and a near-neighbour Coulomb repulsion. It is shown that there indeed both charge and orbital order close to the half-doped region coincident with a layered magnetic structure. Although the orbital order is known to drive the magnetic order, the layered magnetic structure is also favoured in this system by the lack of coherent transport across the planes and the reduced dimensionality of the lattice. The anisotropic hopping across the e_g orbitals and the underlying layered structure largely determine the orbital arrangements in this region, while the charge order is primarily due to the long-range interactions.

The low energy part of the vibration spectrum in PbMg_1/3Nb_2/3O₃ (PMN) relaxor ferroelectric has been studied by means of neutron scattering above and below the Burns temperature, T_d. The transverse acoustic and the lowest transverse optic phonons are strongly coupled and we have obtained a model for this coupling. We observe that the lowest optic branch is always underdamped. A resolution-limited central peak and quasi-elastic scattering appear in the vicinity of the Burns temperature. It is shown that it is unlikely that the quasi-elastic scattering originates from the combined effects of coupling between TA and TO phonons with an increase of the damping of the TO phonon below T_d. The quasi-elastic scattering has a peak as a function of temperature close to the peak in the dielectric constant while the intensity of the central peak scattering increases strongly below this temperature. These results are discussed in terms of a random field model for relaxors.

Composite film containing titania electrostatically linked to oxidized multiwalled carbon nanotubes (TiO₂-s-MWNTs) was prepared from a suspension of TiO₂ nanoparticles in soluble carbon nanotubes. The structure of the film was analysed principally by Fourier transform infrared spectroscopy, scanning electron micrography and x-ray diffraction. The optical and electrical characterizations of the film were investigated by UV–vis spectrum, photoluminescence and photoconductivity. The enhancement of photocurrent in the TiO₂-s-MWNT film is discussed by taking the photoinduced charge transfer between the MWNT and TiO₂ into consideration.

Analysis by D L Sidebottom of the dispersive frequency response of the real-part of the conductivity, σ'(ω), for many alkali phosphate and metaphosphate glasses, using a fitting model involving a 'universal dynamic response' power law with an exponent n and a constant-loss term, led to anomalous n behaviour that he explained as arising from variable constriction of the local cation conduction space. In order to obtain adequate fits, he eliminated from the data all low-frequency decreases of σ'(ω) below the dc plateau, ones actually associated with electrode effects. Such a cut-off does not, however, eliminate electrode effects possibly present in the high-frequency part of the data range. The results of the present detailed analysis and fitting of both synthetic data and several of his experimental data sets show unequivocally that his anomalous n behaviour arose from neglecting electrode effects. Their inclusion, with or without data cut-off in the fitting model, leads to the expected high-frequency slope value of n = 2/3 associated with bulk conduction, as required by recently published topological effective-dimension considerations for dielectric relaxation in conductive systems. Further, the effects of the inclusion in a full fitting model of series and possibly parallel complex constant-phase-element contributions, representing electrode and nearly constant loss effects, respectively, have been investigated in detail. Such composite models usually lead to best fitting of either the full or cut-off complex data when they include the semi-universal, topologically based K1 bulk model, one indirectly derived from the assumption of stretched-exponential temporal behaviour.

New filled skutterudites LnFe₄P₁₂ (Ln =  Ho, Er, Tm and Yb) and YRu₄P₁₂ with heavy lanthanide (including Y) have been prepared at high temperatures and high pressures. Electrical and magnetic properties of these compounds have been studied at low temperatures. The magnetic susceptibility of HoFe₄P₁₂ and ErFe₄P₁₂ follows the Curie–Weiss behaviour at higher temperatures. The linear slope of χ⁻¹ versus T curves yields effective magnetic moments of 10.43 μ_B for HoFe₄P₁₂ and 9.59 μ_B for ErFe₄P₁₂. These values are in good agreement with magnetic moments of Ho³⁺ and Er³⁺ ions calculated from Hund's rule, 10.60 and 9.69 μ_B, respectively. HoFe₄P₁₂ shows a ferromagnetic transition at around 5 K. TmFe₄P₁₂ and YbFe₄P₁₂ exhibit the paramagnetic behaviour at low temperatures. The lattice constant of YbFe₄P₁₂ is 7.7877(5) Å, larger than the value expected from the skutterudite compounds with the oxidation state of +3. This compound may be in an intermediate valence state. YRu₄P₁₂ shows the superconducting transition at around 8.5 K. This compound is a new superconductor. The T_c of YRu₄P₁₂ is higher than that of YFe₄P₁₂ and YOs₄P₁₂, and is highest among the metal phosphides with a skutterudite-type structure.

The crystal structure and magnetic properties of ternary oxide Na₂TbO₃ were investigated. This compound has a monoclinic structure with space group C 2/c. The cations form two kinds of layers, one of which is composed of Na and O atoms, the other consisting of Na, Tb, and O atoms. In the latter, the Tb ions are arranged in a honeycomb manner. Powder x-ray and neutron diffraction measurements show that a partially disordered arrangement has been found between Na and Tb ions (∼20%). A broad peak of the magnetic susceptibility against temperature was observed at ∼60 K, which is due to a two-dimensional characteristic of the magnetic order of the Tb ions. At lower temperatures, this compound shows an antiferromagnetic transition at 38.3 K. The magnetic structure of Na₂TbO₃ was determined by powder neutron diffraction measurement at 2.6 K. The magnetic moments of the Tb⁴⁺ ions (∼6 μ_B) order in the collinear antiferromagnetic arrangement.