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Abstract We report on the strong changes induced, by confinement, in the microstructure of the semiconductor poly(2,5-bis(3-hexadecylthiophen-2-yl)thieno[3,2- b ]thiophene) (PBTTT) and its photovoltaic blend with [6,6]-Phenyl-C71-butyric acid methyl ester (PC 71 BM). These organic compounds can be used as model systems to illustrate how sensitive this class of materials can be to spatial confinement on device-relevant length scales. The spatial confinement of nanofilaments as a function of diameter, from 180 to 25 nm, has been investigated by X-ray scattering with nanofocused synchrotron beams. The effects of spatial confinement are evident by crystallization in different crystal forms, reduction of crystallinity, phase segregation and anisotropic crystal orientation. It is also shown that confinement is an efficient tool to direct the overall texture included the crystal orientation of the homopolymer PBTTT and the PBTTT/PC 71 BM blend in a controlled manner. Graphical abstract Image 1 Highlights • Solution template wetting allows the fabrication of polymer and hybrid nanowires. • Confinement in PBTTT and PBTTT/PCBM nanowires has been studied by X-ray nanoprobes. • Confinement induces phase segregation and different crystal forms in hybrid nanowires. • Interaction of organic semiconductors with template walls directs the overall texture. [ABSTRACT FROM AUTHOR]

Samples with inversion parameter values (δ) ranging from 0.27 to 0.14 while maintaining the crystallite size value have been successfully fabricated from commercially available powders by mechanical grinding and thermal annealing treatments at temperatures ranging between 400 and 600 °C. Detailed characterization studies of these samples using X-ray, neutron diffraction and magnetic measurements have confirmed for the first time the simultaneous coexistence at 2 K of short range antiferromagnetic and ferrimagnetic ordering for a wide range of the inversion parameter. The magnetic phase diagram obtained is different from the one previously reported, which shows at 2 K the coexistence of long range antiferromagnetic order and short range order for values of inversion parameters less than 0.1 and the presence of a ferrimagnetic order only for values of δ > 0.2. At room temperature, the Rietveld analysis of NPD patterns and the magnetization curves showed a paramagnetic behavior in the samples with δ ≤ 0.1. For the samples with higher cationic inversion, typical hysteresis curves of ferrimagnetic materials were observed and the saturation magnetization values obtained agree quite well with the net magnetic moment obtained from the Rietveld refinement of the neutron diffraction patterns. [ABSTRACT FROM AUTHOR]

Transformation of deuterated ethanol from the plastic crystal phase into the monoclinic one is investigated by means of a singular setup combining simultaneously dielectric spectroscopy with neutron diffraction. We postulate that a dynamic transition from plastic crystal to supercooled liquid-like configuration through a deep reorganization of the hydrogen-bonding network must take place as a previous step of the crystallization process. Once these precursor regions are formed, subsequent crystalline nucleation and growth develop with time. [ABSTRACT FROM AUTHOR]

Abstract Magnetic properties of PrCuAl 3 and NdCuAl 3 single crystals, adopting the tetragonal BaNiSn 3 -structure-type, are reported. Our magnetization and specific heat measurements revealed no magnetic ordering in PrCuAl 3 , while NdCuAl 3 orders antiferromagnetically below T N = 2.45 K. The paramagnetic regime was investigated for both analogues revealing (i) the a-axis as the easy direction of magnetization with (ii) a relatively high uniaxial anisotropy energy of 13.2 meV for PrCuAl 3 compared to a smaller value of 4.7 meV for NdCuAl 3. The measured data are well explained by rare-earth ground state multiplet splitting in crystal electric field. A powder neutron diffraction experiment confirmed PrCuAl 3 to remain paramagnetic down to 1.5 K. On the other hand, NdCuAl 3 orders antiferromagnetically below T N with an incommensurate magnetic structure described by two propagation vectors k 1 = (1/3 - δ 1 , 0, 0) and k 2 = (1/7 - δ 2 , 1/7 - δ 2 , 0), where δ 1 = 0.035(1) and δ 2 = 0.007(1). The magnetic moments (of both magnetic modulations) are arranged within the basal plane with a small z-component moment allowed by the symmetry. Our results are discussed with respect to other R CuAl 3 compounds. Graphical abstract PrCuAl 3 and NdCuAl 3 compounds were investigated by magnetization, specific heat and powder neutron diffraction measurements on single and polycrystalline samples, respectively. Physical properties well fitting into the theoretical frame of rare-earth element (R) in crystal electric field were compared with previous results on CeCuAl 3 – another member of R CuAl 3 family. Magnetic structure of NdCuAl 3 was determined to be described by two propagation vectors and magnetic moments confined to the basal plane, however with symmetry allowed out-of-plane tilt. Image 1 Highlights • PrCuAl 3 and NdCuAl 3 single crystals were prepared. • Magnetization and specific heat data are well described by crystal field model. • No magnetic order was observed in PrCuAl 3. • NdCuAl 3 orders below 2.45 K with an incommensurate magnetic structure. • Obtained results are well consistent with other RCuAl 3 compounds (R = rare-earth). [ABSTRACT FROM AUTHOR]

Topochemical nitridation in ammonia at moderate temperatures of cation ordered Sr2FeWO6 produces new antiferromagnetic double perovskite oxynitrides Sr2FeWO6−xNx with 0 ＜ x≤ 1. Nitrogen introduction induces the oxidation of Fe2+ to Fe3+ and decreases TN from 38 K (x = 0) to 13 K for Sr2FeWO5N which represents the first example of a double perovskite oxynitride with both high cationic order and nitrogen content. This synthetic approach can be extended to other cation combinations expanding the possibility of new materials in the large group of double perovskites. [ABSTRACT FROM AUTHOR]

The microstructure of high temperature shape memory alloys of the Ru-Ta and Ru-Nb family are investigated in detail. After cooling from the high temperature cubic β phase the off-stoichiometric alloys show a compound twinning in the tetragonal β′ phase which prevails at room temperature and can be observed as two levels of laminates A and C [1]. The stoichiometric alloys are characterized by a second phase transformation from β′ to monoclinic β″, which adds another type of twinning. The latter belongs to the monoclinic P2/m structure and has been created out of one of the lost symmetry elements from the tetragonal P4/mmm phase during the β′ → β″ transformation. The unusual characteristic of this new twinning, called B, is the fact that it has an intermediate size between the A and C twins that belong to the high-temperature transformation β′ → β″. This is due to a second constrained martensitic transformation. [ABSTRACT FROM AUTHOR]

Among all antiferromagnetic transition metal monoxides, NiO presents the highest Néel temperature (TN ~ 525 K). In this work, the size-dependent reduction of TN in NiO nanoparticles with average diameters (D) ranging from 4 to 9 nm is investigated by neutron diffraction. The scaling law followed by TN(D) is in agreement with the Binder theory of critical phenomena in low-dimensional systems. X-ray absorption fine structure measurements link the decrease of TN to the occurrence of size effects (average undercoordination, bond relaxation and static disorder) in the nearest and next-nearest Ni coordination shells that hold the key for the maintenance of the antiferromagnetic order. [ABSTRACT FROM AUTHOR]

Among all bi-magnetic core(transition metal)@shell(transition metal oxide) nanoparticles (NPs), Ni@NiO ones show an onset temperature for the exchange bias (EB) effect far below the Néel temperature of bulk antiferromagnetic NiO. In this framework, the role played by the magnetism of NiO at the nanoscale is investigated by comparing the microstructure and magnetic properties of NiO and Ni@NiO NPs. With the aim of bridging the two systems, the diameter of the NiO NPs (~4 nm) is chosen to be comparable to the shell thickness of Ni@NiO ones (~2 nm). The EB effect in Ni@NiO NPs is attributed to the exchange coupling between the core and the shell, with an interfacial exchange energy of Δ E ~0.06 erg cm −2 , thus comparable to previous reports on Ni/NiO interfaces both in thin film and NP morphologies. In contrast, the EB detected in NiO NPs is explained in a picture where uncompensated spins located on a magnetically disordered surface shell are exchange coupled to the antiferromagnetic core. In all the studied NPs, the variation of the EB field as a function of temperature is described according to a negative exponential law with a similar decay constant, yielding a vanishing EB effect around T ~40–50 K. In addition, the onset temperature for the EB effect in both NiO and Ni@NiO NPs seems to follow a universal dependence with the NiO crystallite size. [ABSTRACT FROM AUTHOR]

Abstract: Ru-based high temperature shape memory alloys show different structures at different temperatures and composition. Equiatomic Ru–Ta and Ru–Nb show two subsequent phase transformations, but their individual influence is still unclear because of the difficulty of comparing the high temperature cubic phase, the intermediate tetragonal phase and the low temperature monoclinic phase. It is important to find a way to compare these structures in order to better understand the microstructure of these alloys and their shape memory behaviour. In order to get the necessary information the alloys have been investigated with neutron diffraction technique during in-situ heating up to about 1100 °C. This study shows the evolution of the lattice parameters and the shape of the unit cells at different temperatures for the three phases these materials exhibit. It proposes a way to compare the different structures and it gives a mathematical expression of the phase transformations. The ultimate goal of this work is to enable a better understanding of the deformation mechanisms in the unit cell and a possible anticipation of the existence of a shape memory effect in these systems. [Copyright &y& Elsevier]

The antiferromagnetic (AFM) transition of the normal ZnFe2O4 has been intensively investigated with results showing a lack of long-range order, spin frustrations, and a "hidden" entropy in the calorimetric properties for inversion degrees δ ≈ 0 or δ = 0. As δ drastically impacts the magnetic properties, it is logical to question how a δ value slightly different from zero can affect the magnetic properties. In this work, (Zn1-δFeδ)[ZnδFe2-δ]O4 with δ = 0.05 and δ = 0.27 have been investigated with calorimetry at different applied fields. It is shown that a δ value as small as 0.05 may affect 40% of the unit cells, which become locally ferrimagnetic (FiM) and coexists with AFM and spin disordered regions. The spin disorder disappears under an applied field of 1 T. Mossbauer spectroscopy confirms the presence of a volume fraction with a low hyperfine field that can be ascribed to these spin disordered regions. The volume fractions of the three magnetic phases estimated from entropy and hyperfine measurements are roughly coincident and correspond to approximately 1/3 for each of them. The "hidden" entropy is the zero point entropy different from 0. Consequently, the so-called "hidden" entropy can be ascribed to the frustrations of the spins at the interphase between the AFM-FiM phases due to having δ ≈ 0 instead of ideal δ = 0. [ABSTRACT FROM AUTHOR]

Abstract.: One of the simplest ways to confine polymeric materials is by self-assembling during the crystallization process. The remaining amorphous phase is then constrained by the lamellar crystals. In this manuscript, we aim to shed additional light in the understanding of the amorphous chains dynamics of semicrystalline polymers above the T by using incoherent quasielastic neutron scattering QENS in a nanoscopic time scale (10-10s) on poly(ethylene terephthalate). The observed dynamics is satisfactorily described by a theoretical model that considers that the proton mobility follows a random jump-diffusion in a restricted environment. We demonstrate that the combination of macroscopic with nanoscopic dynamic tools allows a complete description of the confined dynamics on a paradigmatic semicrystalline polymer like poly(ethylene terephthalate). Graphical abstract: [ABSTRACT FROM AUTHOR]

Combining different experimental techniques, investigations in hexagonal P63/mmc Er2Fe17 show remarkable magnetovolume anomalies below the Curie temperature, Tc. The spontaneous magnetostriction reaches 1.6 x 10-2 at 5 K and falls to zero well above Tc, owing to short-range magnetic correlations. Moreover, Er2Fe17 exhibits direct and inverse magnetocaloric effects (MCE) with moderate isothermal magnetic entropy △SM, and adiabatic temperature △Tad changes [△SM ~ --4.7 J(kgK)-1 and △Tad ~ 2.5 K near the Tc, and △SM ~ 1.3 J(kgK)-1 and △Tad[1 ~ --0.6 K at 40 K for △H = 80 kOe, respectively, determined from magnetization measurements]. The existence of an inverse MCE seems to be related to a crystalline electric field-level crossover in the Er sublattice and the ferrimagnetic arrangement between the magnetic moments of the Er and Fe sublattice. The main trends found experimentally for the temperature dependence of △SM and △Tad as well as for the atomic magnetic moments are qualitatively well described considering a mean-field Hamiltonian that incorporates both crystalline electric field and exchange interactions. △SM(T) and △Tad(T) curves are essentially zero at ~150 K, the temperature where the transition from direct to inverse MCE occurs. A possible interplay between the MCE and the magnetovolume anomalies is also discussed. [ABSTRACT FROM AUTHOR]

Abstract: We have synthesized the intermetallic YPrFe17 compound by arc-melting. X-ray and neutron powder diffraction show that the crystal structure is rhombohedral with space group (Th2Zn17-type). The investigated compound exhibits a broad isothermal magnetic entropy change ΔS M (T) associated with the ferro-to-paramagnetic phase transition (T C ≈290K). The |ΔS M | (≈2.3Jkg−1 K−1) and the relative cooling power (≈100Jkg−1) have been calculated for applied magnetic field changes up to 1.5T. A single master curve for ΔS M under different values of the magnetic field change can be obtained by a rescaling of the temperature axis. The results are compared and discussed in terms of the magneto-caloric effect in the isostructural R2Fe17 (R=Y, Pr and Nd) binary intermetallic alloys. [Copyright &y& Elsevier]

Recently, potential technological interest has been revealed for the production of magnetocaloric alloys using Rare-Earth intermetallics. In this work, three series of Tb x R 1 − x Cu 2 (R ≡ Gd, La, Y) alloys have been produced in bulk and nanoparticle sizes via arc melting and high energy ball milling. Rietveld refinements of the X-ray and Neutron diffraction patterns indicate that the crystalline structure in all alloys is consistent with TbCu 2 orthorhombic I m m a bulk crystalline structure. The analyses of the DC-magnetisation ( M D C ) and AC-susceptibility ( χ A C ) show that three distinct degrees of disorder have been achieved by the combination of both the Tb 3 + replacement (dilution) and the nanoscaling. These disordered states are characterised by transitions which are evident to M D C , χ A C and specific heat. There exists an evolution from the most ordered Superantiferromagnetic arrangement of the Tb 0.5 La 0.5 Cu 2 NPs with Néel temperature, T N ∼ 27 K, and freezing temperature, T f ∼ 7 K, to the less ordered weakly interacting Superparamagnetism of the Tb 0.1 Y 0.9 Cu 2 nanoparticles ( T N absent, and T B ∼ 3 K). The Super Spin Glass Tb 0.5 Gd 0.5 Cu 2 nanoparticles ( T N absent, and T f ∼ 20 K) are considered an intermediate disposition in between those two extremes, according to their enhanced random-bond contribution to frustration. [ABSTRACT FROM AUTHOR]

We report on structural and magnetic properties of a SmCuAl 3 single crystal. The sample quality, phase and structure purity were investigated by means of x-ray and neutron diffraction, BSE electron microscopy and EDX analysis. The crystal structure was identified to be of a tetragonal BaNiSn 3 -type (space group I4mm , 107). Magnetization measurements revealed two magnetic phase transitions: from paramagnetic to ferromagnetic state at T c = 28 K and another transition at T N = 6.6 K connected with a development of the antiferromagnetic component of magnetic moments. Both ferromagnetic and antiferromagnetic components are followed down to lowest temperature. Possible origins of the phase transition at 28 K are discussed. Paramagnetic data are well described assuming a Sm3+ ground-state-multiplet splitting in crystalline environment. Crystal field parameters are estimated and used for magnetization and specific heat calculations revealing a qualitatively good agreement with the experimental data. • SmCuAl3 single crystal was prepared. • Magnetization and specific heat data are well described by crystal field model. • Both ferromagnetic and antiferromagnet ordering were observed. • Obtained results are well consistent with other RCuAl3 compounds (R = rare-earth). [ABSTRACT FROM AUTHOR]