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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]

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]

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]

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]

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]

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]